See this plunkr for a demo: http://plnkr.co/edit/fwA6naUUfH55aJTXYVgm?p=preview

Clicking on the element should transition it's width between the values in .small, .medium and .large, but what is happening is that in between a class change (from small -> medium, or medium -> large), it's width is resetting.

Removing the ngAnimate dependency will show the correct behaviour, as will reverting to 1.2rc3, 1.2rc2 and prior. This may potentially tie in with a change discussed towards the bottom of #3587?

The issue seems to be due to a gap in how performAnimation calls the domOperation between $animate.removeClass and $animate.addClass calls, presumably because of separate timeouts? I verified that if the dom operations are performed immediately (in the same call stack), the issue will not occur.