The Omnimax is amazing when you see the movies that were meant to be projected on it--like ""Flight of the Butterflies" and "Born to be Wild."
It's not as great for feature films. I saw Star Trek Into Darkness there recently, and it was eh. When the camera panned down quickly, there was a rush like on a rollercoaster. But there was a large part of the frame that was clearly cut off--I could tell when there was text on the screen especially as about a quarter of letters would be missing.
On the plus, while the movie tickets themselves run $12 a person, the concessions are crazy cheap...like $3.50 for a big popcorn cheap. On the negative, on my most recent visit, they did not honor a discount program I belong to, which was pretty lame.