When it comes to value for money, it is difficult to beat Beatriz's place. It is not a luxurious place by any means, but it is more than you would expect for the price. The key thing is the location: it is three buildings from the beach and it is in Leblon. Trust me, I am from Rio, and Leblon is by far the best place to be in the city.
Beatriz was a very good host (although I did not meet her). She was very attentive and arranged for things to be fixed immediately.
I can also attest that whatever problem with the cleaning of the flat (mentioned in few reviews) is no more. The flat was very clean when I came in.
All in all, I highly recommend it as a no-frills great value flat almost on the beach.