This whole AppStore concept stinks. I hope that it fails, because if it succeeds, they will take it as an opportunity to completely lock down Mac OS X, too. Nobody should purchase software from the Mac AppStore.
What evidence do you have that Apple will do this? Do you honestly think Apple doesn't know the difference between a curated consumer device and a general purpose computer used by consumers, graphic artists, video editors, scientists, etc.?
I'll buy from the Mac app store if the buying experience is superior to buying elsewhere. It's that simple.
Even if Apple locked down the Mac platform one day, honestly, so what? I'll use a Mac as long as it does what I need it to do. If it stops doing that, I'll go elsewhere. I use a Mac because it is a tool to get things done, not because of any free or open principle.