My girlfriend and I stayed for a month and had a good time!
The location is great for Copacabana, everything you need is around the corner (gym, restaurants, supermarket, beach, …). Also, it is quite spacious, but personally I would not recommend it for more guests than 1 couple over a longer period of time.
Sometimes it can get a bit damp, so make sure to open the windows enough.
Overall it worked well for us, but for what it is, it was a bit pricey.