Review is for dinner. Take the free shuttle from Harrah's to the Rio. Luckily I didn't have to wait at all, although a long line formed shortly after I got there.
Rio is your standard for Vegas buffets. They're not trying to be high-end like the Wynn, but they still try to give you a little more quality than Hometown Buffet. Overall, I think they succeed. And plus points for not gouging dinner prices.
It's a great place for families because they have all types of food. Of course, I spend the majority of my time eating crab legs but the rest of the food is decent and filling. I usually hate the cuts of meat at buffets, and the Rio is not an exception. Besides that, I think the food deserves a 4-star relative rating for buffets; I'd come back.