I don't think videos are the best way to learn specifics, but in terms of seeing an overview or "connecting the dots" they work well. Ultimately, the real learning comes from the doing and by looking up stuff from various sources. To get the broad view and idea behind a topic, though, a well produced video can't be beaten.

Given that, I doubt these screencasts would be that interesting if they went into every little detail - but if they gave the viewer enough confidence and interest to know what to look up elsewhere, it could work out well.