I don't know what disaster gaming is on Windows 8, other than the "disaster" Gabe Newell and Valve are making it out to be because Microsoft, they feel, is stepping on their turf. My gamer friend was telling me that Microsoft refuses to work with, so that probably is causing more angst for them. 8 is better than 7 for gaming simply as it's all around more resource efficient.
As for those app, yes, 30 percent is taken. They are the ones providing the store as the host. It's no different than WalMart or Target doing the same. Even then, a good chunk of apps right now are free. There aren't a lot of paid ones.
There's an article that does a good job at reasoning why Windows 8 came out the way it did. If Microsoft made a touch OS, like taking Windows Phone and cut the Phone out of it and put in Tablet like android and ios, we'd have yet another phablet that isn't any better than the others. Now, as they want the world to use Windows 8, that suggests they could be forcing it. Or, it could suggest they want a major change to the PC, so they can continue developing Windows in their fashion.