How did it help you? I mean what were your numbers before and after and how did you track it to your video efforts as opposed to ordinary SEO efforts?
How effective is it? Is it more effective than say, backlinking from article submission sites?
Sorry for the questions, but am definitely interested!
You can easily track the flow of your traffic using Google Analytics (free) - that way you can see if you're getting any traffic referred to your site from YouTube, MySpace, etc...
How effective is it? It's as effective as you make it. Plain and simple.
It really depends on the market, the product and your presentation.
Is it more effective than backlinking from article submission sites? Let me put it this way: flour on it's own doesn't do much. Sugar on it's own doesn't do much. Eggs on their own don't do much...but put them all together, and you have one awesome cake.
(Okay, so I love eggs on their own...but you get the point).
Don't compartmentalize each method so much - you should be mixing it up (not JUST video...not JUST article submission...not JUST directory submission...not JUST social bookmarking, etc....all of them).