John Carter was enjoyable. I watched it with my 16 and 14 year olds. I found the 3D to be unobtrusive, in fact this is the first 3D movie I have seen that wasn't just blatantly horrible about that. I would have rather watched it w/o the 3D though. It wasn't necessary. I'll say that the movie isn't completely true to the source material, but it was true to the spirit of the books. If you want a decent family film to take your kids to, and they're too old for Lorax, I'd recommend it. My 14 year old son wants to read the books now and that's a great thing for a movie to do.
Oh, thou clear spirit, of thy fire thou madest me, and like a true child of fire, I breathe it back to thee.