When the app store for iOS was released my first thought was that the Mac really needed one of these, mostly based on how easy it is to install things through Linux package managers like apt - and of course updating everything easily was nice too.
Over time (and as my experience with OS X grew) I slowly thought that it was less and less of a deal - and that few people were actually expecting a Mac App store, so I guess I just gave up on the idea.
Now it's here though, I can't believe how obvious it all is. They should have had one of these years ago. I don't think there are even rumours at this point, but Microsoft would be mad to not build one for Windows too.
Chopper 2 was #2 on the Mac app store for a couple weeks and the developer says on his blog that it sold 100,000 copies (at 99 cents, mind you) in its first week[1]. So, We can guess #1 is roughly double that.
So, back of napkinning:
100,000 units sold / 7 days = 14,285 copies a day.
You can guess, then, that Angry birds is probably selling 20,000 copies a day at the very least, which at 5 a pop is US$100,000/day gross, 70k net.