As far as I am concerned the Las Vegas Mandarin Oriental is the gold standard for quality and service in Las Vegas.
As well, as it's not priced as high as MO generally is in other places, due to the competition in Las Vegas, it's also an attractive value proposition.
Having stayed with Mandarin Oriental in New York, Singapore, Las Vegas and Munich, I have to give high (highest) marks for the Las Vegas property, and I think it's certainly the best hotel in Las Vegas itself.
Service standards are second to none, and the quality of food, and room are top notch. The attendants in the spa are on the ball and there to help you in any way possible, to the point of you wanting to help them back for being so helpful.
Beds are super comfortable, drapes are controlled by switches on the walls, along with touch screen bedside units (which also control temperature and everything else you can imagine).
Rooms are nicely appointed, if I were to criticize anything it's that the modern architecture results in some oddball dimensions in some of the rooms, but it's very minor. High definition TV sets have great fidelity, service is quick and careful, it's really the closest you can get to being in Asia with Asian standards for service without flying over the pacific.
The spa is welcoming and beautiful as well.
I even remember the last time I stayed here, some years ago, where I gave them some clothes for dry cleaning and they came back in 2 hours instead of the next day. And I wasn't even asking for expedited service.
I can only highly recommend MO Las Vegas, they know how to run a hotel. It's the one place you can go to in Las Vegas where you don't feel like you're one more element of the herd being ushered through the vast machine that are the big casino hotels.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC