I got a chance to visit Red Rock several years ago, literally days after the grand opening.
I only checked out the casino and a couple of restaurants, but can't really comment on the rooms as I haven't stayed yet.
Five stars all the way, although I recall losing quite badly here in a very short timeframe.
If booking a stay, be sure to check out the rules for incidental deposits and resort fees - this place is top notch, and I'm sure their requirements are much higher than the norm, as the case is with Green Valley Ranch.
Definitely recommend, although you might have a bit of better gaming luck at Arizona Charlie's Decatur a few streets down.