I bought StarCraft II today. It took me an hour or two to get it running with Wine, mostly because of some out of date lib32 packages in Arch. It might save you some time to know that if you enable the multilib repo in Arch, be sure to pacman -Syu first, because you may have installed some lib32 libs prior to enabling that repo.

To get StarCraft II displaying well in xmonad, you have to change some settings in winecfg and in the game itself.

WINEARCH=win32 winecfg

In the Graphics tab, select a desktop size of 1678x1024 if you're on a dual screen 1680x1050 setup, with a 20px xmobar and a 24px Tabbed layout on the game desktop. When in game, go to the Options screen and select Windowed (Fullscreen). You should get something like below.

If you have skipping sound (like I did,) in winecfg select "Emulation" under Audio > Hardware Acceleration.