My opinion on this goes somthing like this... Yeah, you might be able to parrot the gross movements, but you may miss subtlety like angles or whatnot that will make the technique, um, lets give it the benefit of the doubt and call it "marginally effective".
From experience, I cant tell you the number of times I have been, in the presence of my instructor and shown a technique, and gone, "Oh ok" and done it... wrong. Then he does it to me... and its like a lightbulb switching on. THAT is one of the big things a video lacks, is having an experienced coach to "put the hurt on you" so you know what it should feel like when you do it to someone else, AS WELL as to point out mistakes you dont see... Again, numerous times I'll be working with a partner and think I have a technique down, and he will come and say "do it to me" and break the technique... then show me a small change to avoid that. Valuable lessons no video can teach.
