I saw the film and liked it, although Hellboy did battle the doggy(s) a few too many times. Then I saw this DVD and bought it on the strength of the film.
I liked a lot of the elements of this DVD such as the musical score, use of mythology and particularly using the actors from the film - fantastic voices.
I thought the animation could have been of better quality (I really mean the frame rate), but I guess this puts costs up. The CGI of the clouds in the storm towards the end was bad, but many other things were fantastic (plane crash, many of the big baddies, the heads).
I gather they could not use the drawings from the original comics so had to come up with a new look for the characters. I quite liked the new shapes of the characters, although I guess it will not be to everyone's taste. After about 10 minutes I found myself drawn into the story and semi-forgot it was a cartoon.
Did I say I really loved the music/score/sound effects and how they meshed with the film?
A bit more character development, plot intricacy and quality for the cartooning and I would give it 5 stars, but I do like cartoons.