I'm also using XMonad on Arch Linux. I found it hard to setup correctly, but once it is, it's a real productivity booster. Firing up another terminal (Meta-Shift-Enter) and not worrying about it's position is a time saver.

If you want to try it out, I can help you by reducing the time needed to set it up. My dotfiles are here: https://github.com/wunki/wunki-dotfiles

Best nuggets for your setup can be found in xmonad.hs, xinitrc and Xdefaults files.