The newly launched Mac App Store may sport a familiar, iTunes-like face. But there’s still plenty to discover beneath the surface of Apple’s new source for buying software. We’ve been wandering up and down the store’s virtual aisles, so here’s our in-depth guide to shopping the Apple way. Get clicking.

If you want to start shopping, the first thing you need to do is upgrade to Mac OS X 10.6.6, an update to Snow Leopard. If you aren’t running Snow Leopard, you won’t have access to the Mac App Store. Once you’ve installed this, you’ll find an App Store icon has appeared in your Dock, right next to the Finder. (You can also access the store from the Apple menu, top left of your screen.) That’s a different approach to what Apple used with its iOS App Store, which you access through iTunes on the Mac. But the layout of the Mac App Store is similar to what you’ve become accustomed to with Apple’s retail outlet for mobile apps.

Buying apps is a similar process to shopping in the iOS App Store. When you want to buy something, you enter in your iTunes ID and password and, boom – it’s purchased. The app downloads automatically, and what you bought is installed directly in your Applications folder and placed in the Dock. (You can drag it out of your Dock later, or Control-click and deselect Options > Keep in Dock, if you prefer not to have it on show there.)

The Mac App Store features an iTunes-like interface

When it comes to cost there’s a lot of variability among the Mac App Store apps. There are free apps, of course. But then there is no uniformity of pricing, Apple’s Aperture is £44.99, Things and Acorn cost £29.99, Delicious Library sells for £23.99, OmniGraffle Pro will set you back £114.99, and Distribute is listed at £399.99. Apple has priced its iWork apps at £11.99 each (twice the cost of the iPad versions but a great price compared to the bundle price in the physical world), and its iLife apps at £8.99 (allowing you to buy just one of the apps in its digital life suite). Some developers have cut their prices, while others have kept them the same. It will take a while for people to figure out the right prices for Mac App Store apps.

You will be able to use iTunes Vouchers to pay for applications bought from the Mac App Store. If you’ve got a gift card to redeem, you can just click on Redeem in the Mac App Store and enter your codes, just as you would in iTunes or in the App Store app on iOS devices. It is essentially the same account.

Already installed
The Mac App Store is clever enough to recognise if you are trying to buy a third-party app that you already own, at least some of the time. If you already own a particular application, when you browse the Mac App Store, instead of a button with a price, you might see a button labelled ‘Installed,’ which prevents you from making an impulse buy. Note that this doesn’t work with all apps – the store is just looking for apps with the same version number and ‘bundle ID,’ a unique identifier, in all the apps installed on your Mac.

However, in practice sometimes this doesn’t run smoothly. Some developers changed their version numbers on the apps they submitted for the store, others changed only the bundle ID but kept the version number, while a few left everything alone. This is why some installed apps appear as Installed and others don’t.

After you update Mac OS X, the App Store app will appear in your Dock, next to the Finder

This situation is somewhat confusing, and the blame seems to lie at the feet of Apple. The problem arises from the fact that when the Mac App Store was announced, Apple didn’t tell Mac developers who wanted to put their wares in the store whether they should use the same bundle ID for the Mac App Store version that they use for their existing app or create a separate one – never mind that the two versions of the software may be, for all intents and purposes, identical.

It’s not necessarily a good thing if the Mac App Store does recognise that you already own an application. A problem can also arise when an existing application is recognised as installed and the developer then updates their app in the Mac App Store, because your version will no longer be registered as Installed. So in order to receive updates through the Mac App Store i seems you would need to re-purchase it from there.

Licence transfers
At this time, Apple offers no sort of system for transferring a licence you already own for an app into the Mac App Store. This is partly why some developers have gone out of their way to offer highly discounted prices for a limited time at the store’s launch. They want to encourage users who prefer the Mac App Store way of updating software to opt into the ecosystem.

We didn’t buy Aperture from the Mac App Store, but it knows it’s installed

For now, our advice is to be careful not to purchase software until you decide that you want to opt into the Mac App Store ecosystem, perhaps when there is a major new version or the developer has a sale. Many developers have stated that they will maintain separate, non-Mac App Store versions of their software and update them, at least for some time, for users who cannot or do not want to buy into the Mac App Store. A few developers, though, have moved their apps exclusively into the Mac App Store, and slashed their prices, at least for a limited time, to help with the transition.