I just saw it yesterday. I enjoyed it thoroughly, but those kinds of movies are generally up my all. (It should be noted the first two movies I saw in a theatre were Return to Oz and The Black Cauldron, so I suppose the seed was planted young. Also, I'm a big fan of Terry Gilliam, which ties nicely into this film.) I can see why people would either love it or hate, despite myself falling into the former category. I didn't particularly have any problem suspending disbelief for it, and honestly didn't recognize the actor playing the lead until the credits, as I hadn't looked at who was in it other than Tilda Swinton before going.
Also, the classroom scene is now one of my favorite scenes of all time.