I've seen three movies in 3D, and my reactions varied.
How To Train Your Dragon did it right, and really enhanced the film, especially the flying scenes (I saw it in 2D the day after, so the comparison was quite easy).
Alice In Wonderland did it wrong, and the clunky effort kept breaking my suspension of disbelief.
Avatar was a mix; parts were done very well and added visual depth to the scene, and others were done very poorly and made me upset. The opening shot in particular, with the camera pulling focus from the floating bubble to Jake's face was probably the biggest offender, since it almost gave me a screaming headache when my eyes kept trying to focus on the now very out-of-focus bubble.
Personally, I see 3D as sticking around for a while (another 2-3 years), before fading into the background as a niche market, but I doubt it'll disappear entirely like the last few efforts at 3D movies have. The glasses are a big stumbling block, especially for anyone who already wears glasses (I wore my contacts to all three, knowing I was going to be wearing the glasses). Until that can be overcome, I don't think 3D will become any kind of standard, let alone requirement.











