The fabulous return of Franka Potente!
This is a great little creepy movie about staying in the subway way past the time you should have left.
The monster is great, with backstory and hinted-at relatives (who could easily return for a sequel!). The locale is the London subway system, a place that I assure you is well up to the task! The characters in the film are largely temporary, but you do get to know them (and probably like them) while they last. The effects are very well done, with only the required amount of gore.
There was one thing that really bothered me about the story though. The monster has been down there all this time, that was made fairly clear. Why do all these people get killed on this particular night? I would assume that the monster hasn't been killing a dozen people a night for the past couple years, why start now?
In a lot of creepy films, the story starts when the main characters "unwittingly unlock the prison that has contained the evil all these years". There's a reason for that.
All in all though, thoroughly enjoyable.