This is definitely a minority opinion, but I think the first season of Doctor Who was the best. William Hartnell's sinister characterization of the Doctor is very underrated, and he was well-supported by excellent companions - particularly Ian and Barbara, who are the most convincing representations of "normal" people in the show's history. Sure, the Doctor's granddaughter Susan was a criminally under-used character; but here in The Sensorites, she gets to shine a little by defying the Doctor's wishes and using some cool telepathic powers.
I'm also a fan of season one because of the (generally) great scripts. And while The Sensorites is far from the best-written story of the season, I do think that Peter R. Newman's script features some compelling ideas. In defiance of Doctor Who conventions, Newman depicted the Sensorite race as mostly benign and sympathetic creatures (an interesting contrast to the show's usual "evil monster" aliens); indeed, the Sensorites only do "bad things" in this story in order to protect their planet from exploitation by humans who want to strip-mine the place. In a sense, then, this is the sort of left-wing (or at least politically aware) story that didn't become commonplace for Doctor Who until the Pertwee era.
The story's production design, meanwhile, is pretty good (given the era and budget). The Sensorites may look a little fake, but to me they're perfectly respectable aliens by 1960s TV standards; certainly, Doctor Who produced much stupider-looking aliens even in the 1980s (like the Ergon, to name one of many). Also, the set design for the human spaceship is effective, and enhances the tense and claustrophobic atmosphere of the opening episodes. Unfortunately, both the set design and the pace of the story take a bad turn once the action shifts to the Sensorite planet, but the drop in quality is not nearly as bad as some critics suggest.
In short, The Sensorites is an interesting story that lacks energy sometimes; it's not a classic, but it deserves to enjoy a somewhat better reputation. Unfortunately, given the lowly status of this tale in the Doctor Who canon, the BBC didn't put too much effort into giving us a great DVD. The special features, though not bad, are rather thin. The most interesting featurette involves Doctor Who fan Toby Hadoke investigating Peter R. Newman's background; he uncovers a surprising amount about the little-known writer, including some genuinely emotional material. Unfortunately, this feature is undermined slightly by Hadoke's snarky "I'm a self-aware sci-fi geek" persona. Also featured is a short interview with Doctor Who's vision mixer, which is less boring than it sounds.
While I wish I could give this DVD four stars, the presentation is pretty bare-bones and the actual story has a few flaws. So I'll settle for three stars, but it's more like three-and-a-half. If this is arguably the worst story of Who's first season, that's a testament to how strong the era really was.