Latest Safari on OS X 10.8.2 in a Macbook Pro w/ Retina
Wow. So it works for me and I'm using Opera. This reversal has to be some kind of first for me...
Opera is (was?) pretty good about supporting all the latest cool toys. Demos/PoC's normally worked well, productionalized products not so much.
There has been a very obvious Chrome|Safari|Webkit only trend recently, usually for either demos/pocs, but also often for MVP/betas (I believe Mega may have been one of those).
You can enable WebGL in Safari. Go to Preferences -> Advanced and click "Show Develop menu in menubar". "Enable WebGL" is the last item in the Develop menu.
Kudos.
I believe it's not enabled by default because there are still some security vulnerabilities present, is that right?