A few thoughts: I watched this movie years back when I had really bad claustrophobia and it was pretty creepy up until the creepers showed up. But watching it now, it's hard for me to even focus on it due to how poorly executed the tension is. It once felt very atmospheric and intense, but after coming back to it, I'm surprised at how cheap most of the scares are here, and how unremarkable the claustrophobic scenes now feel. Neil Marshall is a director who knows how to inject thrills into his projects, and this is one example of a movie that feels very much "injected", as the many attempts to startle the audience feel pretty forced and half-assed. The way this movie is shot and edited doesn't allow for the monsters to do much other than ham it up and scurry towards the screen in a very visibly, rapidly sped-up and corny fashion. It's all a bit silly, though I do appreciate the practical effects and lighting.
Who would I recommend it to? Fans of horror movies where things jump out and scream at you should find this scary.