I saw this twice, in 3d and Imax. Do not see regular (not that it is bad but because it is so good you want to make your 1st experience that much better). The animation was so good and imax was a better than 3d in visuals and sound but when i saw it 3d i sat middle of theatre and when i saw in imax my wife sat us in the far back (mistake).
Seeing it in the back of the theatre with such great 3d allowed me to see the edges of the screen alot more and ruined the effect a tad. Not saying to be a front row joe, but try and sit middle to upper middle for this in 3d or Imax for best effect.