OmegaX: I buy games from a lot of different stores like GOG, Steam, GamersGate, D2D (RIP), and Amazon but I won't be buying from the Windows store and I doubt any major publisher will be dumb enough to ditch other stores to sell exclusively on it.
timppu: Why wouldn't you buy anything from the Windows Store?
The interesting part is that apparently Windows Store will be the only possible way to deliver Metro apps and games, even if they are freeware. So at least for them, either you use Windows Store, or can forget about publishing it to Windows devices (AFAIK). Sure, "normal" PC games and apps can still be delivered by other methods, but maybe in the long run "normal" Windows games will become obsolete the same way like DOS games became when the publishers finally ditched it in favor of Win32/DirectX.
It's not really different what Apple is doing with their exclusive app store. All the companies publishing games and apps for IPads and IPhones don't seem to care about ditching other (non-existent) stores, as long as they get big sales.
EA is a different story because they are already trying to push their own delivery system, they will not abandon it without a fight. And maybe Half-life 3 will be Steam exclusive as well, at least at first.
If I wanted a OS brand store for all my applications and games (Hint: I don't) I'd have bought a f-ing Mac. With portable devices like smartphones and tablets I let them get away with it because they aren't as versatile as a PC. I'd hate if MS forces its own AppStore on PC users and we let them do it.