Saw it last night.... I thought it was an entertainingly funny good adventure of a "B" film. And I mean that as a compliment. The Hellboy motif of comedy amidst the Cthulhu-ism is retained pretty nicely. Some of the sub-plots are kind of soap-opera-like but I think that's intentional ... in some way it was like watching an action sci-fi anime with romantic twists.
Some very nice stunt work - I understand the character Mr. Goss plays worked for seven months with swords and spears (and wire) to get that skill level of choreography.
Probably the worst thing I could say is that to someone steeped in this sort of stuff - the plot will be predictable and there's a fair amount of MiB smirking in the first part.
And O gods, I *love* the tooth fairies...