I went to see this on Saturday and thought it was really good. I didn't know a great deal about the guy before hand but thought he was protrayed as a lovable, comical type of man rather than Britains most dangerous prisoner. It did remind me of A Clockwork Orange for some reason...
After a little reading around since watching the movie, there are obviously inconsistencies as is the norm for movies like this, but I don't think they really detract from the movie.
If you get a chance to see it, I can recommend it. I found it very entertaining and actually funny in places.