Just got back from seeing it.
Imo, the 3D only hurt the movie. It wasn't the type that benefits from the gimmick. If anything, that was the only part that disappointed me - not the 3D, but the fact that this movie didn't have a lot of badass effects or action. I was hoping for a lot more color and bizzare "trippy" shit. It was dark like a Burton movie would be, but not wild enough, and lacking the visual treats. I was also expecting more from the characters.
Parts of it were slow, and the movie itself is literally dark, lots of gray, and dull, hazy colors, to the point of almost being nap-inducing. The storyline is served up as new, but it's really the same.
I can put my disappointment aside, realizing that it was only because of my own expectations that I'm let down. Once past that, I must say it was a pretty decent movie. The Cheshire Cat was cool, and Johnny Depp was perfect for the stage that he was put into. Still, it could have been a lot better, I think.
This is all coming from a big Burton/Depp fan. I can see where a lot of people wouldn't like it much at all.