Overall, it was a good stay. However, there are a few things to note.
Pros: Location in Leblon is hard to beat. The apt is also a full complex, so you get access to the pool, gym (old, but functional), a restaurant inside the building, Wi-Fi in common areas, 24/7 concierge and security. There are also two malls literally a 2 min walk from the apartment - and the beach is a 5 min walk. The apartment is small but comfortable for a couple.
Cons: Very limited amenities if you're there for more than 2/3 days. There are not many cooking essentials/or kitchen items. The apt itself is pretty outdated, clearly hasnt been renovated in a long time. This is ok though for the most part, I'm not too picky so I didn't have a problem with it. A big con that I did have and I think it's something for remote travelers to note... is that internet is very basic, and pretty slow. If you need to do more than watch a Netflix film before bed, or respond to a few emails - you will feel the pain. I'd recommend buying a portable router or something if you need to work while you travel.
Also, host is not responsive. I pinged him about the internet and never got a reply.
Overall: I think the apartment is a great value to be honest, and I would stay there again. I think you just have to be cognizant of the drawbacks. Seems like the host knows he puts the apartment at a fair price, that it's in a good location, and that the building is great - so he doesn't seem to really care too much about it/invest in it.
Anyways, take it for what it is. Overall I'd say a good stay.