I know why you're here. You're wondering "Should I see Le Reve or O?"
You've only got the time/budget for one water show while in Vegas, so I'm going to make this very, very easy on you.
See O.
There.
Le Reve isn't bad at all. It's fun and artsy and worth the price of admission. There are a few "wow" moments, but when you're in a town this competitive in the live entertainment sector, you gotta keep me on the edge of my seat the whole time.
Le Reve is ambitious, with the whole theatre-in-the-round/dance thing, but that ambition limits the stage settings and ability to create interesting special effects. Most of the acts are rehashed versions of previous acts in new costumes with new characters.
Sitting way up front isn't a great idea, as lots of the action happens in the air. I recommend choosing a seat closer to the center or back of the theatre.
I don't wanna seem like I'm harping on Le Reve. It's fine. It's just not as much of a spectacle as I was led to believe.