In our iOS 8 release date article we've got all the information you need to know about iOS 8, Apple's next iOS operating system for iPadiPhone and iPod touch, and its imminent public launch.

That's right: iOS 8 has launched at last. iOS 8 became available to download at 6pm in the UK on Wednesday 17 September.

Find out what to expect from iOS 8 - Read our full iOS 8 review and here’s how to install iOS 8 without deleting anything

When is iOS 8 coming out in the UK?

After months of waiting iOS 8 is finally out. iOS 8 was first unveiled to a global audience at Apple's WWDC 2014 event at the start of June, where Apple showed off new features in the next operating system for iPad and iPhone. (Among these: Family Sharing, interactive notifications, predictive typing and third-party keyboards, iCloud Drive, and a new programming language for developers. For full details of all the new features in iOS 8 view our iOS 8 Tutorials zone.)

Then, during the September keynote presentation at which Apple unveiled the iPhone 6 and iPhone 6 Plus, as well as the Apple Watch, Apple announced that iOS 8 will be available to download two days before the new iPhones launch to stores. (The iPhone 6 and iPhone 6 Plus go on sale on Friday 19 September.)

As expected there was a rush on Apple's servers at first. When iOS 6 launched many people weren't able to upgrade for around a day after the new OS became available, and there were even some glitches - apps going missing and the like. The launch of iOS 7 wasn't much smoother, with chaos as people in the States left work early in order to go home to update as their work servers couldn't handle the downloads only to discover that it was Apple's servers that were struggling. Not surprisingly there were more traumas this year, although the biggest complaints were how much space was required to perform the update. More on that below.

We usually advise readers to wait a day or two before upgrading, both to avoid the rush and so they can hear any early horror stories that might put them offf upgrading on a particular model.

More info on iOS 8:

Should I upgrade to iOS 8?

You need to weigh up the advantages and disadvantages of upgrading. We absolutely think it's worth upgrading, but consider these points: 

Pros of upgrading to iOS 8

Getting access to new features, basically. There's lots of good stuff, but here are our highlights: Voice messages; Family Sharing; Health and HealthKit; Widgets; New typing features (whole-word predictive typing and third-party keyboards); Third-party implementations of Touch ID (although obviously this only applies to you if you're on an iPhone 5s, iPhone 6 or iPhone 6 Plus).

Read The best new features in iOS 8: Eight reasons for iPad and iPhone owners to upgrade today!

See below for more details of iOS 8's new features.

Cons of upgrading to iOS 8

It will be very hard to downgrade back to iOS 7 (or earlier). One of Macworld's most popular articles is a tutorial explaining how to downgrade from iOS 7 to iOS 6, even though the process is exceptionally awkward and often impossible. Lots of people get caught out in iOS updates and find themselves unable to go back. Check you definitely want to do this before taking the plunge. (Reading our iOS 8 review is a good start.)

Your device may get slower. But this only applies to the lowest rung of compatible devices (the iPhone 4s and iPad 2) and we can't test this until the full version of iOS 8 launches this evening.

When iOS 7 came out, iPhone 4 users founds their devices got significantly slower - that was the weakest device that was rated iOS 7-compatible. This was partially addressed with the iOS 7.1 update, but this writer's old iPhone 4 remains slower now (on iOS 7.1.2) than it ever was on iOS 6.

Older devices won't get the full range of features - not really a con, just a weakening of a pro. Combine this with the above and it might be enough to convince those on relatively old iPads and iPhones to hold off on their upgrade for a few weeks at least: long enough to see if other people on those devices are finding speed reductions with the new OS.

Read: How to speed up your iPhone.

How to upgrade to iOS 8

If you decide that upgrading is right for you (and as we said, we would recommend this for everyone on an iPhone 5 or later and an iPad 3 or later; iPhone 4s and iPad 2 owners might wish to wait for a while), then how do you upgrade to iOS 8?

It's actually very easy. You should get a notification informing you that a new version of iOS is available for you to download; all you need to do is confirm that you're happy to do this. You'll need to download it, and then install it; the whole process is likely to take a couple of hours, but this all depends, as we say, on the amount of server traffic and how well Apple is coping with it.

If you don't get a notification you can look in the Settings app and see if there's an update waiting for you. Click on the Settings app icon (the silver cogs) and scroll down to the General category. Then tap on the Software Update option (the second one down), which incidentally will have a little grey '1' if there's an update for you.

iOS will think for a moment and then present you with the update, including the amount of storage space required (you may need to clear some space before downloading) and a link to a 'Learn more' article that tells you about the changes. Simply confirm you wish to upgrade and follow the steps.

Upgrading to iOS 8 is free. 

The video above shows you how easy upgrading to iOS 8 can be - although as you will see from the video in this story about upgrading iOS 8 over iTunes, it's not always such an easy process.

For more detail on the upgrading process: How to update your iPhone or iPad to iOS 8.

How much storage space will iOS 8 take up?

Based on last year, we expected that iOS 8 would be about 700MB, although at the time it was recommended that you have 3GB free.

Unfortunately it's iOS 8 turned out to be even bigger and greedier. iOS 8 is 1.1GB and requires a massive 5.8GB of storage to be free before it can install. This is because it downloads a compressed file, unpackages it and then installs it. You need the space for the unpacking and the update. It also needs enough space for iOS 8 itself.

Luckily you can download the software via iTunes, and connect your iPhone to your Mac to instal it on your iPhone without needing to delete apps, photos and more. We explain exactly how to go about updating iOS over iTunes on a Mac or PC in this article: Here's how to update to iOS 8 without deleting anything.

Af for how much space the update uses - we had a 16GB iPhone with just 1.3GB available. The iPhone's capacity was shown as 14.91GB before and after the update. Once our software was up to date and we had 917MB of space left over sot he update didn't use up 1.1GB more than iOS 7 did, it was around an additional 300MB.

New features in iOS 8

Reachability

There are a number of new features in iOS 8 designed to make one-handed use easier, these new Reachability features are specifically for users of the bigger iPhones. We don't believe they will be available to users of 4-inch or smaller iPhones.

'Reachability' is Apple's name for this update: it means that when you double-tap the Home button, the entire screen interface shrinks downwards so you can reach it easily. It's a clever idea, and shows more than a little humility.

Messages

The Messages application in iOS 8 includes a new voice messages feature. And it's pleasingly gesture-sensitive: you lift the iPhone to your ear to listen to the message, for instance, speak your response, and then move the phone away to send your message. Read: New Messages features

Health and HealthKit

Fascinating range of health- and fitness-related apps and data compilation features that take advantage of the capabilities of the new M8 Motion co-processor. Read our Complete guide to Apple's Health and HealthKit.

Touch ID

Can now be used with third-party apps, which opens up a wealth of new possibilities: e-commerce apps, for instance, would be able to build in fingerprint authentication, and other apps could use fingerprint identification to replace tedious passwords and logins.

One new first-party implementation of Touch ID is Apple Pay - see below for more on that. Read: How iOS 8 will unlock Touch ID

Photos

Read about the new features in Photos for iOS 8including Time Lapse, new smart adjustments and filters, and photo storage in iCloud.

Notifications

Work with third-party apps. Notifications are also now more interactive: you can tap on a notification for a Facebook status update, for instance, and you'll be able to 'like' the status or comment on it from there, wthout having to go into the Facebook app. Read more about iOS Notification Centre.

Safari for iOS 8

Find our more about Safari in iOS 8 including new Private Browsing and the ability to scan in your credit cards.

Keyboards

We're pretty excited that Apple will be adding new keyboard features and allowing third party keyboards in iOS 8. Read about Using QuickType & Swype keyboards in iOS 8 plus: Alternative keyboards in iOS 8.

Apple Pay

Apple Pay is Apple's new wallet technology (turns out it's not called iWallet).

Apple Pay uses NFC, a hardware feature that is included in the new iPhone 6 and iPhone 6 Plus. It also works in conjunction with Touch ID and a "new secure element" that stores all payment information securely. In fact, thanks to a system called tokenisation the information stored isn't even your account details but a set of codes used to unlock those details.

Anyway, Apple Pay will allow you to pay for goods and services with your phone's Touch ID. It will work in the US at launch; UK start date of this service is to be confirmed but is expected some time early next year.

The new Apple Pay API is now open to developers to incorporate into their apps.

More: Apple Pay FAQs: Will Apple Pay work in the UK, is Apple Pay secure and more questions answered

We're continually updating this article... Stay tuned for more information.

You'll find the rumours from before iOS 8 was unveiled on page 2.