Hi Ori,
You can use the Sunspider Javascript Test
http://www2.webkit.org/perf/sunspider-0.9/sunspider.html
or just read the review ( like I do) - the reviewer says 15% faster than 3.57 and three times faster than FF 3.0
http://blogs.zdnet.com/hardware/?p=6836&tag=nl.e550
Either way its a great improvement
Cheers
Jay