I agree that windowed it has better/more performance than when playing full screen. When playing fullscreen, your dead meat because of the lagging (because of 100% cpu usage) when playing windowed you got some more killing chance, it works better, but still the performance for me is not good enough to play it as i like (with bootcamp it works great). But it would be great to play this full screen, maybe in future releases it will become better.
I tried using firefox 3.5, but besides it wont launch before clicking like 1000 times refresh, it has no difference in performance or improvement of the menu when returning from a game. So count that out.
In short, lets hope in future releases this gets better.