To OP also: FYI, you may want to make sure you get those tickets early... they tend to sell out pretty quickly also - we did see many people 'standing in the stand-by lline' and 'disappointed' that even concierge couldn't get them tickets.
We saw "O" during our stay at Bellagio.. great stage/water thing.. typical Cirque.. 'darker' than most of the Cirques, I'd say.. can be a little hard to follow in beginning.. but, we liked it.
Another ++ for Blue Man Group.. best 'show' I think I've ever been to, personally.