Well, the idea of an app store isn't really all that bad, look at linux distributions like Ubuntu: they've got an application "market" thing integrated. Okay, just ignore the fact that you can't *buy* anything.
The awful thing (like always) is that you're not the one controlling which applications you *can* install anymore. Steve Jobs gets to dictate which applications are allowed in the store and which not. There's been a lot of controversy about the app store in iOS, and I can guarantee this'll be the case for the OSX-store.
Sidenote: I'm not too keen on Apple, but as with all things: you have to be objective.
PS: I'm dutch, so I apologize if there's anything wrong with my English. :)