I agree that it is a right tool for the job type of situation but I think there are many times when canvas is that tool for certain types of games. I understand the complexity of the Aves engine and what they are trying to do - but their performance needs are greater than most of the other games out there.
I think for simple tile-based games (pac man, mario bros, bejeweled) and casual 2d games (side scrolling shooters, puzzle games, angry birds) canvas is a really easy way to go.
Really? Why would you bother with Canvas at all if you were doing anything (non-rotating) sprite-based?
Canvas' main advantage is that it can render vector graphics. Beyond that it's useful for doing image rotation in a cross-platform way and for manipulating bitmaps. If your game doesn't require those things, I can't think of a reason you'd want to use it in favor of something the browser is so natively good at as laying out image-based scenes.
These days, I'm much more inclined to use 3d-accererated CSS Transforms and Transitions first, then fall back on CSS positioning, then finally Canvas/SVG as a last resort for the few things that can't be accomplished by CSS/HTML.
I think for simple tile-based games (pac man, mario bros, bejeweled) and casual 2d games (side scrolling shooters, puzzle games, angry birds) canvas is a really easy way to go.