I highly recommend this apartment if you are planning on visiting Rio. We were skeptical about renting an apartment vs. a hotel, but it is a much more economical option and we had no hitches at all. The owner is a very professional and reliable guy, speaks impeccable English, responds to emails in a timely manner and has proper paperwork and documentation of your transaction with him. He was also helpful in guiding us to the nearest ATM and pointing out interesting spots to check out.
The listing pictures and description are accurate - although the building is run-down, the little studio bedroom apartment has been done up nicely and is well-suited for visitors. It's a nice, well-maintained space with a well-working A/C unit, plenty of blankets and hot water in the shower. There is also free wifi. The only downside to this place was that the bed is two twins combined, which was not the best option for a couple.
Location is pretty awesome if you're looking to be close to Copacabana. This apartment falls exactly between Copacabana and Ipanema beaches. If you go left, you're at Copacabana beach in less than 5 minutes walk. If you go straight, you'll hit Arpoador, which is a great area for surfing and watching the sunset. To the right you'll hit the restaurants and shopping strips of Ipanema or Ipanema beach in a 10-15 minute walk. There are also a lot of taxis that shoot past here often, so catching cabs is no issue either, and you def need to catch one to get to Leblon.
On a side note, the apartment building is on a quiet street, so it's not a good idea to be walking back too late by yourself - much safer to take a cab. With that said, Rio is actually not nearly as dangerous as most travel reviews make it out to seem. Just take the same precautions you would in any big city and you'll be fine.