Here's a beefed up and fullscreen version of the Ghost Shooter demo: (man, just can't get enough of ghosts and shootin')
I'm interested in framerates both restored and with the window maximized for Firefox 5 and Internet Explorer 9 on your machines, if you have them don't mind a quick test. (You can also hit F11 to go fullscreen on most browsers.) I believe both browsers should have pretty good hardware acceleration and so should run 30+ fps, hopefully! Right now I think all other browsers would struggle with it.
Let me know your results. I get 50-60fps on IE9 always, and only about 14fps on FF5 (because they blacklisted my driver so I don't get hardware acceleration).