I saw mib3 and it ruined the film for me and my wife. It was the first 3d film I have seen since jaws revenge and I hated it. Slow moving stuff was fine but when someone was in the middle of the shot and someone moved around them, they were blurry where they wouldn't be in 2d version.
I'm looking forward to seeing the film again in 2d.
They showed the trailer for the new spiderman and it was terrible in 3d. The area of focus was so small it felt like I was watching the screen through a telescope.
There's your problem though. MIB3 wasn't a true 3D film. It was one of those horrible conversions.
I really feel for people that watch one of those type of films without realising it. Especially if it's their first 3D experience...

Honestly, it is so much better than that. But it's only worth seeing one or two films a year in 3D. Usually because there is only that many films per year that actually warrant 3D. Often they are sci-fi films...