I submit that while you can watch all DVD's you want, you will not learn technique from a DVD.
Indeed, a lot of the subtleties of what actually makes the technique work can easily be missing, and its easier to have live instruction at the beginning to help you better understand these points.
[again, the whole question of what making a technique work means is a whole different story with Aikido.]
After you gain certain concepts the DVDs become more useful... though live practice with Aikido really is what helps the most in understanding what does and doesnt work.
I will add I do enjoying learning the differences between the systems... or rather trying to figure out what they have in common, which turns out to be what makes the techniques from each style 'work'.