@ those saying Compositing slows down Game performance... this is what the whole "Ubuntu fixes Unity Redirect fullscreen" news was all about... Games that go full screen present [b]directly[b] (ie, avoid compositing) to the backbuffer. This is mostly likely what Windows does. IDK how Mutter/Muffin/Gala/Xfwm handle this, but even if they don't do it now, there's nothing stopping them from following along.
Also, watch the Wayland presentations. Wayland handles this automatically where any "top-level" window gets dynamically turned into an undirected surface (at least that was my understanding).
Also, "finally available games" is wrong, there are games for GNU/Linux since always...
Running a game works like a treat on Windows. On Linux, developers can't even see why fullscreen, exclusive control over the screen is actually useful for games. They think a game is just nethack running in xterm or something. They've come up with countless standards, like notifications, systrays, redundant IPC implementations, but they can't be bothered about a standard for getting fullscreen control for gaming.
Sometimes it's rather hard to tell that they're not actually actively trying to sabotage Linux for gaming.
i tried kde out again 2 weeks ago. i didn't liked it. but what annoyed me the most was that i could get tearing free video playback. well, after a search via goodle i found out how to "fix" kwin for this, though i didn't tried it. i couldn't stand the de anyway. there is absolutely nothing i liked and a lot i dislike and want to get rid of it.
but this is my taste and my needs, except for the not working vsync in fullscreen xbmc. that's a really unaccaptable thing.