Watching Derek Wyatt's screencast was very motivating when I switched from TextMate but I don't think I've learned much from his videos. Everything goes too fast, you can't really move around the video in an intuitive manner and the guy is too distractingly funny.

Forcing myself to use Vim everyday for everything for a few weeks (and all the vim-related googling that ensued) sure helped me a lot more than these screencasts.

But again, those are very exciting and it sure helps to stay excited when you have a mountain to climb.