"Are We Taking CSS Too Far?" I would say yes. I first had thoughts like this when Webkit introduced CSS animations. Something like an animation seems to me to be a behavioural concern rather than one of presentation, and thus belongs in the JS layer.

Pragmatically speaking I don't mind CSS animations as much since they can do things that are non-trivial to pull off convincingly in JS, e.g. 3D transforms. I also understand CSS animations are, or imminently will be GPU accelerated too.