I agree completely with Federico.

Clicks and touches are instantaneous, you only know that a button is pressed when your finger is all the way down on that click. There’s no time to animate it.

Unfortunately with all the cool CSS3 toys, a lot of people are overusing transitions. Personally I love transitions that are in the 200 millisecond range. Just enough to make it look "smooth" but not so much that it feels slow. Snappy elements are almost always better from a user experience standpoint.