The instructions from the wiki for Unity-2d integration also work fine: http://haskell.org/haskellwiki/Xmonad/Using_xmonad_in_Unity_...

That runs xmonad with the unity panel; it doesn't add the launcher, but I was never a fan of that to begin with (in part because its interaction with xmonad wasn't great, but I never spent much time trying to get it working properly either so it might be possible). The key difference is the wiki assumes you're installing from cabal, where-as Mark's assume an apt-get installation which already comes with a .desktop file.

Note that the wiki instructions mention the need to explicitly add gaps at the top, which Mark's instructions didn't. (Also, that the wiki config doesn't actually launch the launcher!)