We saw the 3D version also and felt ripped off. Nothing in the usual pop out at you 3D rendering was seen by us. Enjoyed the movie very much though.
I thought the 3D was excellent. I appreciated there were no cheesy objects being thrown at you.
So, would you guys say that it's not necessary to watch it in 3D?
well as my posts would tell you, YES.
I took my 3 year old son (well, 2 years, 263 days) to see it as his first ever theater movie. He enjoyed it, but obviously did not "get" it. As for me, I enjoyed it thoroughly. It was far deeper than I expected it to be, but in a good way. As usual, the opening Pixar short film was nothing short of outstanding as well.