Whilst this is clearly an off topic subject for Palm Sounds it does touch on some issues that already exist for iOS app developers. Issues like paid upgrades and demo apps.
I imagine that Apple must be thinking about these issues for the Mac store if not for iOS. I mean, would Apple just give away updates to iLife forever if you’d bought it once? I don’t think so. And what about their Pro applications, I can’t imagine they’d want to restrict themselves from some kind of upgrade pricing.
I think that something like this would need to be in the Mac App store, and if they can make it work there then why not in iOS?
My guess is that they are struggling with issues around how to make it fair for customers. What I mean is, the mechanics of upgrade pricing and what is fair as a priced upgrade and what isn’t. I should think that would be quite tough to work out.
Anyway, these responses on TUAW are probably very typical of what lots of developers are thinking right now about the Mac store and the app store too.