Just after Apple announced iOS 7 we asked a number of developers to share their thoughts about the new iPhone and iPad operating system. Generally feedback was very positive, although there were some concerns, with one developer suggesting the redesign of iOS might be like marmite, you'll either love it, or hate it. There were also suggestion that iOS 7 was taking inspiration from Windows Mobile and Android.

Another concern was that the rules for icon design implemented by Apple would make it difficult for developers to distinguish their apps from others. Now the main concern appears to be whether iOS 7 will be ready for prime time when it launches on Wednesday.

We spoke to our developer contacts again to find out whether there is concern or excitement about the launch of iOS 7 on Wednesday. They share advice about upgrading, news about new apps using new iOS 7 features, and trepidation about whether iOS 7 will be ready for primetime. 

[Read our iOS 7 for iPhone & iPad preview.] 

Is iOS 7 going to be ready in time?

The Gold Master version of iOS 7 was released to developers last week. As a rule the GM version should be as good as ready, but there are concerns that this version is not ready for release and that some people will experience issues with the final version of iOS 7 and some older iOS devices when they download it on Wednesday.

One of our developer contacts told us: "When I first took a look at the beta for iOS 7, I was worried. It had more rough edges than any prior first iOS beta I'd seen from Apple. A lot more. I'm impressed by how far they've come, but to be perfectly honest, the GM version of iOS 7 is still beta quality. While it runs mostly well on the iPhone and iPod touch, it has performance issues on older models (the iPhone 4 and 4S) and there are still some appearance problems and crashes. The battery life on my iPhone 5 is pretty terrible. I'm getting maybe 2/3 of what I used to get under iOS 6."

He added: "On the iPad, it's a mess and not at all ready for general release, especially on the iPad 3. The unresponsiveness, drawing issues, and crashes are much worse on the iPad. Because of the state of the OS, I've yet to update my personal iPad, so I don't have a good feel for battery life as the units we use for developments are usually tethered with the USB cord."

His advice: "For both the iPhone and iPad, I would wait until at least the first update before upgrading. For the iPad, I might wait even longer."

CEO of Boinx Software Oliver Breindenbach also has some concerns. He said: "There is a good reason for the proverb 'Never change a running system' [or 'if it ain't broke don't fix it']. Any time there are fundamental changes to an operating system, it is likely that things are going to break. Developers have their work cut out for them - a mad scramble to fix bugs started last week when Apple released the Golden Master to developers. Now, all hope that the bug that affects you is going to be fixed before the release is gone and it is your job to make sure that the apps get fixed."

Binary Formations owner Kevin Hamilton also noted potential issues uncovered by the GM: "Our existing apps seem to run just fine under iOS 7, though developers have only had access to the GM for a little under a week now so we still have some more testing to do."

Another developer said: "I guess that any new iOS is a new bug source..." 

[Wondering what time iOS 7 will be available? Read: iOS 7 release date: what time on Wednesday?]

Working with iOS 7

Some developers have some concerns about their apps when it comes to the update. Marketcircle CEO Alykhan Jetha told us: "With business apps, there is always a little bit of trepidation when a new OS is released - especially when there are so many changes."

However, he admitted: "We are mostly excited about iOS 7. Considering the whole UI change, I was not expecting Apple to release it so quickly. However it looks like they pulled it off."

Despite his concerns about the GM, CEO of Boinx Software Oliver Breindenbach told us: "The transition to iOS 7 will be remarkably painless. I did not find any apps that were broken on my devices, except for our own StopMotion Remote Camera app for which we already submitted a fix that should be available in time."

MacAce CEO Gary Hall experienced no issues getting his apps to work with iOS 7. He told us: "We've been testing our current MacMate app with iOS 7 since the first beta and it's worked flawlessly. In fact, I've not really had any issues with any of my Apps on my iPhone at all." 

BeLight Software told us: "There shouldn't be any reason to have any unstable apps. Developers have had access to iOS 7 for quite some time now and have had plenty of time to push out updates that support the new system." 

Another developer mentioned that some apps don't yet support the new keyboard. 

Bringing iOS 7 features to apps

Back in June developers expected that redesigning their apps to work with iOS 7 would be a time consuming but worthwhile process. Three months on, how did the process go and what new features can we expect to see?

Many developers are excited about the new features coming to iOS 7 and how they can apply them to their apps. Nik Fletcher of Realmac Software told us: "We’re really excited about iOS 7. We don’t have any concerns about apps and stability as we’ve been thoroughly testing since WWDC - as it happens the new APIs will allow us to make our apps even better. Things like the Dynamics and Physics mean we can make apps that are even more at home on iOS 7, and offer really satisfying interactions and fluid animations/motion - and the fact that apps are launched behind the scenes by iOS to do things in the background means that apps will be doing far less catch-up (think email clients downloading mails etc.) when you launch them. We’ve got Clear for iOS 7 coming (a new version built for iPad - for the first time - and iPhone) and really excited to see iOS 7 launch on Wednesday."

Kosta Rozen from Apparent Software thinks that not updating apps to take advantage of iOS 7 will be a mistake. He told us: "We in Apparent Software think that because of large changes in UI, iOS 7 is an opportunity for developers to 'reshuffle the deck of apps', so to speak. Applications that will be updated to conform to the new iOS 7 look and feel will be perceived as 'good citizens of iOS 7' and will end up much better than those that are left to become stale. Also, it's an opportunity for developers to enter the iOS market with new applications that specifically target the new functionality in iOS 7. For example, we are currently developing a game that benefits from the new developer frameworks that are available in iOS 7." 

MacAce CEO Gary Hall advises against adding too many new features too quickly: "We're busy preparing our next major upgrade. We've absorbed all the new features and API's and are now deciding the best way to utilise these fully. We're probably a bit behind other big developers, but we don't want to rush in and spoil an app that is easy to use already, by putting all the bells and whistles on straight away - a common mistake for other apps soon after a major iOS release."

Binary Formations owner Kevin Hamilton has been working on a new app designed exclusively for iOS 7. He told us that 'Too Phat' is a weight-loss tracking app which aims not just to keep track of a bunch of numbers, but to also show you how your body has changed as you progress toward your weight loss goal. "It is currently with Apple for review and will hopefully be available later this week when iOS 7 releases, " he told us.

CEO of Boinx Software Oliver Breindenbach found that the transition from iOS 6 to iOS 7 was simple. He told us: "Last week, we released the first version of PhotoPresenter for iOS. We used standard iOS 6 UI elements. When we compiled against iOS 7, we found that this translated quite well into a native iOS 7 look and feel, so we were able to move that app to iOS 7 in a matter of minutes. We submitted the update last Thursday (adding a very cool laser pointer feature for good measure) and I am curious to see if Apple manages to review and approve it in time. Our other apps use more custom UI and will therefore require a bit more work."

Should I upgrade to iOS 7

Advice for those racing to upgrade from BeLight Software: "From a user standpoint, it's important to check out when the last update [to your apps] was released and take a look at the version changes to see if they've updated the app for iOS 7. We don't really see iOS 7 affecting Rails. It has a custom interface, so it should be pretty much left untouched. It's going to be interesting, though, to see how some of the new features change the way we shop. Like iBeacons or the fingerprint scanner in the new iPhone. These could be major game changers, which could be great news for developers who have apps that could use these features."

MacAce CEO Gary Hall has the following advice: "Make sure you do a full backup prior to upgrade - which goes without saying, but not to worry too much, Apple has ironed out all the niggles and the vast majority of users will have a trouble-free upgrade."

He continued: "I always advise people to wait until they have an hour or so free before doing an upgrade - might just be me but I like to install and then go through all the prefs and have a good old look around and play with all the settings and features. There's nothing worse than upgrading and then needing to do something urgent (change a setting or something) only to find you don't have a clue how it all works."

"I'd generally do a bit of searching on the net for some articles on what's new and things to look out for. Then I'll go and ask Siri all those new questions - just to bring back that euphoria we all felt when our iPhone first answered us back with something that sounded intelligent and useful. I'll very quickly then determine than Siri is still not as clever or useful as I really want it to be," he added.

We're also expecting Siri to be a disappointment, it's one of our 'Eight things we expect to hate about iOS 7'.

Before you upgrade read: Will I be able to update to iOS 7 on my iPhone, iPad and How to update your iPhone or iPad to Apple iOS 7.

How will the public react to iOS 7?

Binary Formations owner Kevin Hamilton thinks iOS 7 will go down well: "In general the look and feel of iOS 7 is quite refreshing. After having used it for a while, I don't like going back to iOS 6.

Marketcircle CEO Alykhan Jetha told us: "I think they'll be about a two week adjustment period for everybody as they get used to the new UI. After that, I don't expect too many complaints or issues. Those first two weeks are going to be very interesting."

iOS 7 is going to be a big change, in many ways you can expect it to make your trusty iPhone or iPad feel like a completely different device. Our advice if you hate iOS 7? Give it a month

What Apple still needs to fix

iOS 7 offers a lot of promise. But even after iOS 7 Apple will have work to do before developers and App Store customers are completely happy.  CEO of Boinx Software Oliver Breindenbach suggested that Apple should try and fix the App Store next. "Apple gradually opens up access to new OS features for developers with every new iOS version. Apps will get better with iOS 7 if they can leverage those new features. Unfortunately, one thing that has not improved is the App Store itself. Still no paid upgrades (that could help offset the development cost for making the iOS 6 to iOS 7 transition), still a broken ratings and reviews system, still no way for developers to address tech support questions and comments users leave in the reviews, still no good way to discover (and promote) apps. At least Apple has made some good moves that help developers figure out what customers actually bought which makes it easier to transition to a freemium price model while preserving the investment who previously paid for the full version," he said.

What's next: OS X Mavericks

There's another operating system update in the pipeline. One developer expressed concern about progress for OS X Mavericks, rumoured to be available at the end of October. "In general there has been in a noticeable drop in the quality of major updates over the past couple of iOS releases. As an aside, the problem is even worse for OS X, with 10.7 in particularly bad shape until 10.7.4 and 10.8 taking until 10.8.2 before it was release ready. This has seemingly become a trend now and I'm worried it will damage Apple's "It just works" reputation if it continues," he told us. 

Read our preview of OS X Mavericks

Related: 

Forget the iPhone 6: iOS 7 is what will transform your user experience

iOS 7: 22 of the best, most amazing, features coming to Apple's iPhone