Great deal! If you're in town for the weekend, definitely check out Tix4Tonight. I used them for the first time this weekend to see Blue Man Group. We were able to get great tickets center stage for $90. That is about the same price you would have had if you tried to watch the Blue Man Group with a military discount. Actually with a military discount the prices come out to $89 so you're getting a pretty good deal!
We showed up to the booth/stand around 1 or 2 in the afternoon and there wasn't too long of a line. We bought the tickets easily and picked up our tickets at the Venetian later in the afternoon.
There were tons of tickets for various shows on sale at Tix4Tonight in addition to discounts on places to eat! They also had discounted tickets for smaller things like Titanic or CSI for example.
I'd probably come back to them again if I were ever in Vegas and wanted to see a show!