I'm totally switched on to seeing this in a theater now, after all your VERY good words (and James' review of course)!
And, for once, the UK doesn't have to wait two years for something to turn up...it's out this week here too. But I'll probably just catch the flat version: I still don't think a gimmick should make a movie, and for all those that say Avatar was much better in 3D, well, sure the effects and the visuals flying all around will always be cool, but it doesn't make the story, characters or performances any better (or worse) and, indeed, is perhaps what took audiences' perceptions of a lousy script and derivative plot points away from thinking about too much.
Like many have said here, too, the 3D effect doesn't really add much to a film in terms of enjoyment anyway, except for maybe Imax 3D where your senses are truly are fully surrounded. But that it's such a trek and an expensive way to see anything here puts me off going the Imax route for anything less than something I'm literally gaga over seeing: that's right, I'm talking about Tron Legacy!
However, HTTYD sounds like a sure bet for a good night out, and I'm looking forward to it!