Getting between 60-64fps in FF5. Occasionally it will spike to around 55 or so, but not often.
Dual core, Win7x64, 2GB ram, 9500GT
Overall I'm pretty impressed. It wasn't that long ago that I couldn't even run a small embedded HTML5 game in my browser of choice, and now I'm getting good performance at fullscreen <img src="smileys/smiley32.gif" border="0" align="middle" />