It is interesting to compare this low level API to O3D which is a scene graph API from Google (Google also supports WebGL, via the O3D team also, and sees the APIs as complimentary). They are very different APIs taking drastically different approaches. One gives you a new API but a higher level one that may appeal to JS developers more, whilst the other is very familiar to a certain set of developers and would be easier to port work. Ideally, someone will Processing/jQuery-inize WebGL to give it some nice high level love too.
Fun times with 3D and the Web! Great to see WebKit and Gecko doing great things with WebGL already.