I went up during the day ($10 during day, $12 at night). It was super busy so the wait ended up being about 45 minutes, but I liked it up there and ended up staying a bit longer than the rest of my elevator group. The wind felt good on my face and I got a few nice pictures of the Strip (and the traffic on the Strip....).
I just wish the Bellagio fountains had their show when I was up there (instead of just before). I think I would have enjoyed that.