Doctor Who: Boom Town
When US shows do episodes like "Boom Town" they're called "concept episodes". They're the ones that break formula, and do something unexpected. The fans usually love them.
The very essence of Doctor Who, though, is variety. It breaks format with each new story. Or at least it should. In reality it rarely does. The setting, characters and even style may change, but the structure is pretty rigid. In fact, "Boomtown" (with the possible exception of "The Deadly Assassin") is the first true format-breaking episode since "Inside The TARDIS" – and that was only the show's third story, so you could argue that back then there wasn't even really a format to break. The two stories do have many similarities. They are slow-paced, they are talky, they concentrate on characters rather than plot, they are both (arguably) filler episodes, and the TARDIS is a central character in both.
The face-off between the Doctor and Margaret Slitheen is the exotic, full-bloodied, dramatic meat sandwiched between the slight, lightweight action and eye-candy that top and tail the episode. There's a thoroughly watchable vibe of joie de vivre to this TARDIS crew as the episode opens, and whatever your opinion of Jack in his introductory story, you have to admit he's immensely likeable here. The scenes with the Whoobie Gang swinging into action to capture Margaret are huge fun, and there's a wonderful "let's get to work" moment as they stride up the steps of Cardiff's County Hall. The throwaway gag with the Doctor reversing Margaret's teleport device is hilarious, the kind of silly fun (and easy get-out clause) you know you should object to as a serious fan, but you can't condemn because you just know that general audiences are going to love it. Sure, the Doctor could have captured Margaret in a more realistic fashion, but would it have been that enjoyable? This is Russell T at his telly-literate best.
The ending with the TARDIS giving Margaret a second chance – is more problematic, as it's all a little too handy and provides the Doctor with a moral get-out clause. It would have been better to see him forced into making a choice about Margaret's fate. The theme of the story would seem to be redemption. The fact that Margaret is shown sparing a potential victim's life shows that she has the potential for it, but redemption can only truly be achieved with the acknowledgement of past sins. To live your life again with no memory of your previous life is pretty much the same as death; the old Margaret has been wiped out - unless you believe in nature over nurture, in which case it doesn't matter who the Doctor gives the Margaret-egg to, since she'll always grow up rotten. Also weak is the Mickey/Rose subplot. Mickey is becoming a less annoying character, but it's still hard to care about him, as we've seen little evidence of him and Rose actually ever being close. Mucking about in Trafalgar Square for a few moments in the first episode did nothing to convince you that they ever really cared for each other. In various episodes they say they did, but the overriding feeling is that Rose was glad to see the back of Mickey. This makes it difficult to care when Rose feels guilty about leaving Mickey behind (worryingly, since there are indications that this guilt could have some resonance in the final two-parter). On a production level, the Slitheen looked far more convincing than previously, and the direction was tight. Letting things down was a dreadful sound mix, with the music often far too dominant, and some very poor Earth-ripping-apart effects (not helped by the fact that none of the actors seemed to be aware that the ground was crumbling beneath them as they ran across it).
Overall, though, "Boom Town" is a brave experiment, a cost-cutting exercise that makes a virtue of the fact its pennies are being ploughed into the series finale. It will clearly not be to everybody's taste, but if it is to your taste, then there's a lot to enjoy. If nothing else, you have to enjoy the Bad Wolf moment.
Oh, and remember I cited "The Deadly Assassin" as the only other possible format-breaking episode? Its interesting to note just how much fans loathed that when it was first aired. Last place in a season poll doesn't always mean that a story's a dog...