This hostel is amazing. I've stayed there twice, and both times met loads of people I've kept in touch with. The management is very friendly and laid back, and the facilities are fine. You have a choice of air-conditioned or non air-conditioned dorms. I don't remember if they had private rooms or not. There's a good communal room, with a beautiful hardwood floor and internet access.
The location is OK, not wonderful, on a quiet, residential street about three miles north of Copacabana in Botafogo. Buses go to Copacabana and Ipanema from outside. The area seems reasonably safe by Rio standards. You can see up to the statue of Christ the Redeemer (so you can tell whether it's too cloudy to go or not). There are some good restaurants nearby.