Snakedance is one of the most cerebral - and consequently one of the best - Doctor Who stories ever produced. Curiously, fans of the show have a tendency to under-value stories like this one, favoring "action-packed" or "scary" stuff like Earthshock and When a Good Man Goes to War. But, for me, Doctor Who is always at its best when it's being aggressively intelligent. Even now, the BBC can't match Hollywood in terms of action and spectacle; but they can produce good, thoughtful drama like Snakedance, which stands the test of time in every area except production values.
Perhaps the most unusual aspect of this story is that the main antagonist, Lon, is not totally evil as most Doctor Who villains are; he's merely bored and amoral, and so he is easily corrupted by the real villain of the piece, a malevolent psychic entity called the Mara. The Doctor, who is used to fighting more belligerent opponents, has a hard time convincing people that Lon is truly dangerous. Indeed, for most of this story, the Doctor comes across as some ranting doom merchant who is alternatively ignored and locked up by the very people he's trying to help. This makes an interesting - and surprisingly realistic - change of pace from the show's usual formula of making the Doctor powerful and very much in charge.
Christopher Bailey's script is interesting in many other ways, as it touches lightly but intelligently on issues such as religion, family, and our common failure to learn the appropriate lessons from history. Unfortunately, Bailey did not enjoy his experience of writing for Doctor Who (as he explains on one of the DVD special features), and he quit writing both for the show and for television in general; this is a shame, as he is clearly one of the best and smartest writers to take a crack at the series.
Speaking of the DVD, I must reluctantly report that it falls into the "merely competent" category. In the UK, Snakedance was released in a combo pack with Bailey's other Doctor Who story, Kinda; and it seems to me that most of the budget for the UK release was lavished on Kinda, which got a more extensive package of special features, and new CGI effects for the snake-like physical manifestation of the Mara. Snakedance, alas, gets saddled with fewer special features and the same old rubbery version of the Mara. I think it's pretty stupid that they put new Mara effects in one story but not the other, but I guess money was a concern. It's just my tough luck that I've always liked Snakedance more than Kinda!
On another slightly disheartening note, the audio commentary by actors Peter Davison, Janet Fielding, and Sarah Sutton is too caustic and negative for my tastes, and also very repetitive of Davison's past commentaries. I know that many fans like his commentaries precisely because they're critical and "honest," but at this point I'm tired of listening to him constantly complain that Doctor Who needed darker lighting and faster pacing. Yeah, yeah, I noticed that the lighting on old BBC productions is bad when I was five years old - talk about something else already! I much prefer the more thoughtful analysis provided on this DVD by Doctor Who fan/writer Robert Shearman, who actually understands the story (unlike Davison and Fielding) and is capable of deconstructing it in a way that interests me. Bizarrely, the best feature on the DVD - a fairly long chat between Shearman and Bailey, covering a range of cool topics - is buried in an Easter Egg, which is well worth hunting down if you actually like the story and want to hear a cogent analysis of it.