When it doesn't work, that usually means you have to learn implementation details like the digest cycle, which flies completely in the face of having these abstractions in the first place.
Which is exactly why I always hated ASP.Net's page/control lifecycle.. it was nice for windows-ui developers, but really poor when you had to do something custom. Same for MS's Ajax Toolkit. MS is finally learning these lessons. So should everyone else.
If you have simple modular tools that do something well, and you can string them together in a productive way, it's easier to replace certain pieces.
