Strangely enough, I think it's the last of the multi-Doctor stories that I've seen (despite being the first made); though now that I have, I think it's the best of all of them, as a working story. (I probably still like The Two Doctors more, but more because it had Jamie as well as the Second Doctor than because it's actually BETTER than The Three Doctors.)

And the extras are indeed pretty awesome, as with most of the Who range of DVDs. :D