The Other Half and I watched The Descent: Part 2 earlier (SPOILERS FOLLOW). To review it as quickly as possible:
First third: pretty good, and successfully evokes the combination of the vast wilderness of the Appalachians with the claustrophobic terror of the cave system used to such great effect in the first film (and once again, the caves themselves are at least as dangerous an enemy as the crawlers).
Second third: fairly boring. Part of the problem with horror sequels is the difficult tight-rope that always has to be walked. You can't stick too closely to the last film, or the scares will be lessened by simple familiarity. On the other hand, it's far too easy to overcompensate for this and end up chucking in too much new stuff that doesn't sit well with what's gone before, or even helps to undermine it (Tremors 2 parodies this problem by having its giant subterranean worms turn out to be incubation chambers for voracious heat-seeking velociraptor-beetles, or something). TDP2 sticks very much to the first of these options, which really means you're just watching the exact same film again with less interesting characters.
Final third: this actually does something new, by forcing the survivors to start thinking about what - and who - will need to be sacrificed in order to ensure at least someone escapes. There's a scene in which one character is forced to chop off another's hand with an ice axe (a somewhat unergonomic utensil with which to perform the task, to say the least) which is both hideously difficult to watch and probably the most grimly realistic idea in the whole film (why she actually needed to do the cutting is another story).
Plus, Juno is back, which is awesome because a) Natalie Mendoza is astonishingly pretty (even covered in grime and crawler blood) and b) she uses her gymnastic skills in the fight against evil. It also gives Sarah and Juno some closure, which the first film wasn't exactly crying out for, I suppose, but at least lets us know at exactly which point Sarah went mad (so far as I can tell, she escaped from the caves and only her tremendously serendipitous finding of the car wasn't actually real).
Having said all that, the film does have one major problem. It's not the director's fault, or the screen-writers', or any of the actors' (always good to see Gavan O'Herlihy in action, whether he's fighting crawlers, the French, or the Nockmaar army that destroyed Galadoorn).
No. The person to blame is Diablo Cody, because thanks to her, all I could think of whilst watching the last half hour of the film was this:
You win this round, Cody...