I played with it for several minutes and it seemed to work fine for me. I've got a 2010 MBP 17" and i'm running Chrome 11 to access the site.
This is really cool and quite exciting. This is the first WebGL demo that didn't totally max out my CPUs, and still had good interactive performance. I'm really quite impressed.
Thoroughly impressed. I didn't expect it to be so interactive! Lots of fun to be had with reflective surfaces and 'hiding' the light underneath a pyramid.
(using Webkit r83831 on 2009 13" MBP, works a treat!)
I would have like to have seen it working, the image on the home page looks nice http://madebyevan.com/#webgl-path-tracing