I have mixed feelings regarding the new WebGL support with cocos2d-html5 2.1.2. I loved that OpenGL works so fast and with a lot more flexibility than canvas. However, I found several times during development that the screen (in Chrome) didn’t show up when I typed the URL nor when I tried to refresh. I had to cut the URL, open a new window and then paste the URL to have it working, and this happened several times. I don’t know if it’s a Chrome issue or cocos2d issue, I wish I had more experience with HTML5 to help you out. It also doesn’t work when I go to Chrome in the iPhone and type the URL, but it does work on iPad.
I’m releasing a new game on Monday and I took the decision of switching back to 2.1.1. Canvas support, although a bit slow, it gives me more security on its workings (and opens perfectly on most platforms).
Kudos to the cocos2d-html5 team. I’ve been testing the library since less than 3 weeks ago, I have done two games already, and I feel it is as easy to work with as ActionScript 3 (been programming in Flash since years).