I'm with this guy. Canvas is great, but it's an element to include in your scene to render vector graphics, not a container for you to render your scene inside. Often you'll have dozens of them layered about the place, happily doing their thing and unaware of each other. Use it right and it's a great tool. Try to use it as a panacea Flash replacement and you're in for a bunch of headache.
Apologies for going Meta, but the above downvote is the strangest one I've yet seen here. I can't come up with a way to read my comment as inflamatory or "me too". The only thing I can guess is that it's a downvote for disagreement, but without any commentary I can't imagine why the downvoter would do so. It seems like the kind of thing one could easily refute with evidence, if one had evidence that it was incorrect.
I would say canvas is best suited for rendering/processing sprite or pixel-based graphics that does not need mouse interaction, if I had to pigeonhole it. Sure, I've used it via Flot to draw charts, and for purposes that were decidedly vector-ish, but I would never expect to be able to manipulate that stuff without complicated collision data and redraw logic. The API for drawing with the canvas pen is moderately featured but drawing imperatively and trying to act on -mouse interaction just isn't scalable or maintainable.