Be warned that an Apple update will clobber this install. Therefore, you should get the latest X from http://xquartz.macosforge.org/ and install it after an Apple update.
git
My gitk (which uses X) stopped working after the update. I'm not sure if it was the update as I forgot if I ever ran it successfully before the update. Fix: I simply went to the git-osx-installer site on Google Code and downloaded the latest installer under Featured downloads on the sidebar.