First the location for me was perfect. Very secure and quiet area (eg close to Japanese consulate). Many great restaurants in the neighborhood for cheap and higher prices. 5min away to many key places: metro (largo do machado), big supermarket, and van pick up to corcovado (to see Christ the redeemer). Foremost, my favorite, the apartment is 5-10 min away too from Flamengo beach. There you can find many people doing sports and sports facilities.
Aguiar and Sergio were very welcoming, quick responding, and also flexible with the check in/our times.
If anything to improve: the WiFi was bad: slow and not steady. I would have also appreciated some more basic amenities like maybe oil for cooking or toilet paper.
Regardless, I heartedly recommend this apartment!