We spent Memorial Day weekend at the Rio and will definitely be back! We got an awesome deal on rooms and we were very happy with our room in the Ipenema Tower.
Customer service at check-in was prompt and friendly. We had a small issue with the safe in our room and maintenance appeared within about 15 minutes of our calling them - a heck of alot quicker than the service we saw at TI when we had a maintenance issue there!
If you are looking for high-end restaurants or boutique shopping, the Rio is not for you but for us, it was perfect. For high end food, we can head to the Venetian and for shopping to Caesars but see no reason to pay the high price to stay there.
If you do decide to stay at the Rio or even if you don't - check out the Wine Cellar located just BELOW the Masquerade Village. They have a great selection of wine "flights" and great ambiance to go with it.