Firefox beta did an update today to beta 4 and they are "claiming" to be the fastest browser :/...but yeah its beta..though it also has same javascript/html support as the real
Right now though only 2 browsers have hardware acceleration..Opera 10.1 Beta and FF 4 Beta..yeah they are both betas lol and neither support flash yet..
Here I did a comparison of a few browsers and how well they support HTML/CSS/
JS standards:
http://forum.ppcgeeks.com/1996898-post13.html