The Canyon Ranch spa and gym are amazing. Access to the fitness center is no extra charge with the included resort fee if you stay at The Venetian ($28/day). A day pass for the spa facilities alone is $25/day (a total steal!) for Venetian guests. Treatments are obviously extra. The spa and gym were huge, clean, and more impressive than I had anticipated.
At the spa I got a pedicure. Way overpriced/more than my local nail salon at home but totally worth the splurge on vacation. Tricia did my pedi and she was awesome - super sweet, not overly chatty, and did a great job. All of the staff at the spa were great actually.
The spa facilities include a sauna, steam room, hot tub area, igloo room, herbal sauna, etc. There are also many sitting areas with lush couches and settees that have refreshments, magazines, etc. I wish there was more than just water and fruit (because I was hungry!), can't complain though.
When you arrive you get a robe, flip flops, and a locker. The locker room was clean and secure. The ladies facilities were stocked with everything you'd ever need - hair dryers, deodorant, hairspray, powder, gel, etc.
The co-ed areas are really nice and relaxing. The salt grotto and wave room sounded fancy but were just additional sitting rooms - I really didn't notice anything special about them. Still, it is rare to have a co-ed area and I loved spending the extra time with my husband in the spa so I would totally come back just for that reason alone.
Overall, the atmosphere at Canyon Ranch perfect - really inviting and relaxing. I had been a Qua Spa nut but after coming to Canyon Ranch, I may be converted. Qua is slightly nicer but they have jacked their prices way up ($100/day just for the facilities!) and they don't have a co-ed area. Also, Canyon Ranch is just too convenient if you're staying at The Venetian.