Much Better Than Default; Hides Navigation Toolbar; Respects about:config "browser.fullscreen.animateup" Rated 5 out of 5 stars
This is pretty nice. Changing the about:config setting for browser.fullscreen.animateup to "0" makes it less clunky, in my opinion. Like another reviewer on here, I would also prefer it to pop the toolbars over the content and show the menubar when the mouse goes to the top of the screen, but it's not a huge deal. (I have a trackpad set [to 4 Finger Doubletap] to switch between fullscreen/regular, and it's plenty fast).
Works well in Mountain Lion running Firefox 19.0.2