Even more frustrating than what you said (which is very frustrating) - Having already learned ember or backbone or whatever last year, I need to revisit it, or want to use it in my current project because it fits nicely. Or rather it used to. Turns out that in making it better (for whatever the "it" is) they changed fundamental bits on you, in such a way that you basically have to learn another new framework.

Heaven forbid you go back and maintain the stuff written with the old version of the framework...