Just a quick note to warn you all that when browsing the App Store on your iDevice, VoiceOver might not be telling you which apps have in-app purchases.
I just went to check out swackett after allseed's recommendation, and noticed that there was an element at the top of the description which VoiceOver was recognizing but not announcing. After checking, it turned out that this was the text that reads "Top In App Purchases". Presumably this is another iOS 5 bug, and I either hadn't noticed before or I simply hadn't looked at any apps recently that offered these.
Double-tapping on this element takes you to a list of the available in-app purchases, so you can still find out what extra features you might need to pay for.
I'll email Apple's Accessibility Team to let them know.