Eh, the show is okay at best.
Compared to the other Cirque shows I have seen live (Varakai, Quidam, Mystere) it seemed to be a lot more "special effects" then anything else. But then again, I am a love Cirque du Soleil more then most people and have seen their shows so many times I could compare "O" a lot more then other people could.
One thing to note: DO NOT GET LIMITED VIEW SEATS. Get the seats as close to the middle as you can since so much happens towards the back. If you are on the sides you will miss a lot.
For "O" I really didnt want to even give a standing applause since I was so let down.
I went to go see Mystere the next day though, and was completely blown away by it. That one was much better in my opinion.
But, if you have never seen a Cirque show and "O" is your first you won't be let down.
And eat at the Bellagio buffet before the show. If you don't you will be missing the best buffet in the United States.