Avatar was astounding. I'm sure the movie would have been just as well in 2D, but if you have the opportunity, pay the extra $3 and watch it in 3D on the big screen.
This was the first movie I had ever seen in 3D, and boy, am I glad I did. It was everything I had hoped 3D COULD be, but didn't believe it really was. Keep in mind, this isn't your mom and dad's 1970's kind of red-blue-paper-glasses 3D - this is the future of immersive film making.
The plot was rich, the graphics were breathtaking, and the attention to detail was immaculate. I really was wowwed. Definitely recommend any and all friends to go watch. If you only see one movie in 3D for the next year, this is the one to see.