I’ve got a mostly working patch for Homebrew’s Emacs recipe that will build Emacs with a Cocoa interface that supports OSX Lion’s new full-screen mode. I’m posting here so someone else can beat me to it. I know Emacs already has full-screen, this was definitely an exercise in yak-shaving.
It doesn’t quite fill the screen (there’s still some weird height/width calculation bits in EmacsWindow I’ve not gotten my head around yet). It also messes up the screen size when you move back out of full-screen mode.
The following gist includes the full emacs.rb recipe (which adds a command to patch with the above diff).