So the taxi driver says "Are you sure this is the place?", as most Cariocas would not choose Gamboa as a base. Yes the surroundings are interesting, and the walk to and from Centro de Brasil can seem daunting, but it is no worse than many parts of many British or European cities and definitely better than several US cities I have visited.
The staff are unfailingly helpful, the rooms clean but basic, the air con set at 17°C was a bit ott, and the breakfast buffet excellent, room service was basic but fine, again suiting the price point.
This hotels' usp is its location, 10 mins walk to the museum of modern art and the spectacular museum of tomorrow, a 7 min walk to Presidente Vargas metro, the same to Centro de Brasil for the supervia, good local supermarket and fruit shop, as well as the usual chaos of street vendors, yes the area is a bit run down, and try to avoid rooms ending in 16 to 19 as they will be noisier as the busses back up in the peak times. Noise is relative, the lively nature of the area means there is always sound, be it music or traffic.
I look forward to going back.
PS this area is safer than most of the tourist areas, my bag snatch was in Lapa, in Gamboa, tourists are too rare to attract the rio ratboys!