This place was great when it was Oasis and is still pretty good and one of my favorites on the strip. They use to be the cheapest, but since renovations, I think pricing is more in line with the strip. I'm not quite sure what was experienced by the individual that felt they weren't clean.
I like the layout and attention to areas for relaxation. That makes it better than Mirage which doesn't quite have enough space for the chill out and Canyon Ranch which is more oriented toward being a Gym. The lighting is wonderful through out, low enough to make you feel at peace. Also, the ability to grab water and hydrate or to put cucumber on your eyes in multiple places is fantastic.
If you are like me and go to the spa to lounge around for multiple, hours, Nuture is a good one to put on the list.
I still think that the strip doesn't quite pay enough attention to spa in general, so I can't give it the full 5. I mean, go to Asia (half of the Casinos have properties there anyway), check it out and come back and implement all the details.
The only thing I would additionally mention, the spa is FAR from the parking area or entrance areas. You've got a trek if you're not staying at the luxor. Make sure to give yourself a lot of extra time for your appointment to get to the actual spa.