Absolutely fabulous.
I watched Le Reve prior to seeing O and O definitely trumps Le Reve hands down.
The clowns were hilarious! Aye-aye-aye! Their humor was a great contrast to the dramatics of the rest of the show.
The stage is amaaaaazing. It's water then it's a stage then it's both at the same time!
I highly recommend getting the expensive tickets (a pair cost my fiance $340) but you get the best view possible. We were in section 103, row K and not only got a full view of the stage and aerial acts but also you can see the performers facial expressions and intricate movements.
The entire show from start to end was just stunning.
NOTE: This is one of the shows where they take pictures of you at the beginning and you can purchase them at the end of the show in a special keepsake O frame. They're $45 but well worth it. The ones I got came out beautiful and they even had the date on it which means a lot since we saw O on my birthday!!!