I've seen Le Reve four times, and the most recent time I was first row. It could've just been that I was on the right aisle seat and the right time, but towards the end of the show my shirt was quite wet. I got a hoot out of it, but I'd wear something not too fancy, just in case.
That said, I've seen 'O' three times, and while it's beautiful, it can be quite glacial in pace. Le Reve is much faster, sexier, with some great dancing mixed in, and a ridiculously expensive and awesome water/fire finale they installed last year. (Steve Wynn loves to keep his shows fresh.)
"Hey little girls, look at all the men in shiny shirts and no wives!" - Jackie Hoffman, Xanadu, 19 Feb 2008