I have also never tried it -- I will be very interested in following the postings in this thread in hopes of learning the true value of keeping an ad video unit. Sounds like tweakwindows votes a great big DON'T DO IT!
Well, I would not depend on video units, but it does allow you to put a series of relevant videos on your site that may keep visitors there longer. I have a real estate site that is already ranked well and getting normal adsense clicks. I may put this on it and see if there is an improvement or not. I like the way they arrange their sites so visitors can choose which videos to watch without it taking too much space. They even have verticle arrangements for side bars but I am experimenting with the big one. See my sig for an example but that is a brand new site I made yesterday. I will put it on my real estate site later today.