I spent a week at Gustavo's apartment in Catete, and had a fairly good stay. It's a good location if you want to be in the middle of all of Rio's various attractions, between downtown and the southern beaches. It's a short walk to the metro, in a safe neighbourhood, with a lot of shops, supermarkets and bars nearby.
The building is safe, quiet, and in good condition, but be aware that it's two elevator rides and a bit of walking to reach the unit from the street entrance - up to 4 minutes if you're unlucky with the elevator timing.
The unit itself is fairly good. The bed is really comfortable, and WiFi was excellent. The kitchen is well equipped, but very small - for example, it can be a bit hard to figure out where to put the coffee maker when you're using it. The electric heater in the shower didn't provide very hot water during the unseasonably cold June weather, but should be fine most of the year. The window lets in a lot of sunlight, but it's frosted, so you have to open it to get a view of the lovely trees on the property, and then close it before the evening mosquitoes start coming in.
Overall, Gustavo's place is a good option if you're looking for a place to stay in the Catete area.