Okay, this review is only for the Men's spa. Even after I told them I was from Yelp they still wouldn't let me peek into the Women's spa. I asked if there were some tapes I could review. They insisted there were no tapes to review.
The Men's spa is a quiet, relaxing place. Typically uncrowded, the spa features an 8 person capacity hot tub and an excellent little steam room. There aren't a lot of amenities offered, other than the basics: some fruit, bottled water and fruit juice (by request). They stock razors and tooth brushes, but you might have to ask an attendant for them. There's a wall mounted hair dryer available, too.
Expect to pay about $20 a day for admission ($50 for a three day pass), which also gets you into the fitness center. I've never been there (big surprise!) but I'm sure it's nice.
You can get a massage here if you can't figure out how to get to Spring Valley. In addition to the typical hotel style massages, they have recently started offering chair massages. They're not in the comfy reclining chairs you find at foot massage places though. They're in the goofy massage chairs you see at the mall. Pass.
Mikey C says: this is the best spa I know of in Las Vegas.