I almost didn't write a trip report because I agree with a lot of what mecabq posted above. I did have a few different experiences though, from my stay in late March....

Check-in
A complete @#^$show. I arrived around 4pm during mid-week, and there were probably 150 people in a crazy-long check-in line. Fortunately, I'd read about this hotel's VIP check-in, so I walked there...and it was closed. As I came back to the insane line, I noticed there was a "World of Hyatt Guests" mini-line with 5 people in it. It only had one agent handling the line so it took 20 minutes, but at least I wasn't waiting in the main line where many of these guests (rightfully, IMO) were clearly pissed off there were only three agents working and it was going to take them forever. The agent was very nice and when I mentioned I just needed a quiet room and it was my first stay at the Rio, she said "and you're a Globalist too--let's get you a special room!" Although I was here for a conference, I wasn't going to turn down a suite upgrade! My 20 minute wait to check-in was quickly becoming an afterthought!

Room
I took the elevator to the 15th floor to find....I had been given a standard room and with a connecting door, no less. Not that I cared, but my view also looked west, so no view of the Strip or anything. The window curtains were partially torn and I quickly realized the "renovated rooms" here are only partly true. Yes, there's a new tv and the bed felt comfortable, but the bathroom countertop looks exactly like the ones Sheraton hotels used twenty years ago, the toilet was clearly decades old and so was the shower. Because I knew the connecting door would be an issue for me on a three night stay (apparently my assumption of requesting a "quiet room" wasn't understood to mean away from elevators and no connecting door), I waited until after dinner and went back to the front desk to get another room. I don't think the front desk line at the hotel ever had less than 20 people in it during my entire stay, but fortunately my Hyatt line only had two people ahead of me this time. I had the same agent again, and she found me another room but on a different floor & with two beds. I went up to that room, noticed that the HVAC unit was much louder (broken?) but even worse the in-room safe didn't work. So I'm now back at the front desk for the third time in my first day, this time finally getting a non-connecting room with a working safe. I've probably spent 50 minutes in line on just my first day.

Breakfast
Wow, what a mess. The line was already long at 8am, because they were only using seating on one side of the restaurant. It made me repeatedly think how the hotel seemed to be generally so understaffed. There was a Globalist sign, however where it was placed made it completely unclear which line was for Globalists...so everyone used both. The woman seating people was incredibly surly and would just stared at people waiting in line, without helping for long periods. After waiting 15 minutes, it was almost my turn and I finally got a table. I was pretty excited for this food after reading this thread and disappointed when the server told me I could only pick one entree and couldn't add things (like pancakes) to an egg order. The oj was fresh and the food was pretty good, but like higher quality diner food. Better than HH/HP breakfasts for sure, but nothing amazing...many Hyatt restaurants have as good or better food. I almost didn't go to breakfast the next few days because of lines and honestly, if I knew there was a good, inexpensive diner nearby I could've walked into I would've happily done that instead.

Casino/Hotel Lobby
I'm not a big fan of Vegas, so I have very little input here except the place certainly doesn't look new...or great. It wasn't that busy though, so maybe that's a good thing...?

Location
There is nothing except a Walgreens & Chic Fil A nearby. And the Uber/Lyft to the strip is a $12-17, each way. So be sure to factor in that your costs to get to/from 'real vegas' will be at least $24/day.

Overall
This place reminds me--a lot, actually--of the Westin Las Vegas I used to visit in the SPG days (pre 2017). Yes, the Westin has a much better location and isn't nearly as big, but the (lack of) quality is shockingly similar, as is the breakfast. Both places are objectively a dump, and people are either staying there solely because it's cheap or because of their hotel affiliation. If you're staying at the Rio because you're a Globalist paying $30-70/night and that amazing price (along with no resort fee & free breakfast) will help you mentally overcome the issues you're likely to encounter and general low quality of the hotel then you'll enjoy yourself. If you're staying here hoping this would be a good mid-tier Hyatt option in Vegas, you'll likely be pretty disappointed. I've definitely stayed in worse Hyatts (almost all Amerisuites that were converted to Hyatt Places). Would I ever stay in this hotel again? ...not unless I badly needed EQNs and the rooms were crazy cheap. It kills me that Hyatt isn't actively working on getting their own full-service hotel just off-strip (similar to the Westin) and that our options likely won't improve in the next few years.