Except that you have much greater choice of language. Honestly, I dislike client-side web programming because it forces me to use Javascript, even when Javascript may not be the most appropriate language. This would let me choose one of a large range of languages. Definitely a step up.

Secondly, isn't the point of this that it sandboxes native code? That means you can, potentially, have code running much much faster than Flash can.

More choice and better performance = win IMHO.