I thought the first half of it was good, it created the mood of the game really well, it was definately eerie!
Around the last hour I too felt it started to lose the feel somehow, and by the end I really was unimpressed. Pyramid Head definately should've gotten a little more screen time, he was very impressive!
I have to say I thought the dialogue was pretty awful and ruined it a lot for me!
I think that Sean Bean and the male cop shouldn't really have been in the film and the director should've tackled what little meaning they had in a different and more engaging manner... not really much point in them overall.
I think the IGN review of it gets it spot-on!