I was expecting Judy Dench in the car at the end.
The movie was completely ridiculous and over the top...but as others have mentioned it was in line with the tv show in the later seasons. Luther is just completely indestructible, can be stabbed in the gut with a hunting knife then survive several minutes in freezing cold water (sure was lucky the cops had divers with them!) I'll give Neil Cross credit for this: he has a very vivid imagination when it comes to thinking up evil things for villains to do. Andy Serkis might have been the most evil of them all and hey he's a great actor so it was fun. Elba was as watchable as ever too. I enjoyed it, but I wouldn't exactly call it good.
Did they change the reason why Luther was in prison? I can't remember much about the last season of the show, but I was sure he was arrested for Alice's death. But here it was because Andy Serkis exposed him as a dirty cop. Maybe he got away with Alice's death (because she's NOT REALLY DEAD!?) then got locked up again later.