Sunspider benchmark (Win XP, dual core machine):
Opera (v10.53): 299.8ms +/- 1.0%
Safari (v5): 314.2ms +/- 1.7%
Chrome (v5.0.375.55): 326.6ms +/- 7.9%
Firefox (v3.6.3): 716.4ms +/- 1.7%
Firefox 3.6.4 494 IE9 1200 Safari 5 2644 Opera 10.54 3393 Chrome 6.0.437.3 5148
Though it certainly makes great headlines.
Sunspider benchmark (Win XP, dual core machine):
Opera (v10.53): 299.8ms +/- 1.0%
Safari (v5): 314.2ms +/- 1.7%
Chrome (v5.0.375.55): 326.6ms +/- 7.9%
Firefox (v3.6.3): 716.4ms +/- 1.7%