Best of the Best, and its certainly not for the budget-minded people too. You get what you paid for it.
MO Spa sets the standard for what a spa should be. Top-notch facilities and excellent staff (Esp JP in the men's section, one of the best staff I have seem in years of spa experience). It is a whooping $50 on Mon-Thurs or $60 on Friday-Sunday. If you feel like to pamper your body mind and soul, this is the place to be.
Like others mention. They first serve you with tea and exchanged your shoes to their slippers then take you downstair to the spa area. The spa have a nice jacuzzi tub which have curved benches that have bubbles coming from underneath so you can relax while viewing the strip view from the 7th floor. They also have sauna, steam room, laconium room and experience showers that is fun to play with for a bit. There is also a heated stong lounge chairs room and another private relaxation room with fully flat bed. The staff here is really good. They know when to handle you the cold towels when you are in the steam room, placed the dry towel mat outside of your shower without feeling being invaded. This came from numerous years of experience and good customer service mind.
One pet peeve is that they asked you to sign off the bill when you purchase the day pass and they have 3 separate lines where you can write the tip amounts for the staffs (Spa Concierge - for checkin you in, spa attendants and someone else). While their spa is really good, but I think that feels a bit pushy.
Overall, this place is awesome, having tried the spa at MO will make you feel like you will not go anywhere else for the spa anymore. Definitely worth a try and pamper yourself once when visiting Vegas.