I can confirm it's still busted. After a year of Lion I've learned never to bother with the full screen button (that's a feature for noobs anyways right?)
Though what really pisses me off about Mountain Lion multiple monitor is they removed the "Detect Displays" menubar option. Just gone. So now I'm reduced to unplugging and replugging my thunderbolt 27inch display when I connect it to my laptop. F'ing asinine
I personally use cinch to do window management (or at least arrangement) on osx. Mimics Windows' Aero Snap functionality, and does it pretty well. Never had a need for the zoom button.
Though what really pisses me off about Mountain Lion multiple monitor is they removed the "Detect Displays" menubar option. Just gone. So now I'm reduced to unplugging and replugging my thunderbolt 27inch display when I connect it to my laptop. F'ing asinine