Overall a great place to stay for a visit to Barcelona. Location is right in the heart of Gothic Quarter, close to a lot of bars and restaurants. As others have mentioned, it is right above a bar. But we didn't notice it more than once or twice. Especially if you're out late too, you won't hear a thing!
Apartment is dorm-style, with several other guest rooms. You may end up sharing the bathroom with several other guests. Not too big a deal really.
We were there in summer, but there's a ceiling fan and we had an extra stand fan which was great. The bed is firm, but you're probably not in Barcelona to sleep that much anyway.
Host is great, very responsive and helpful, which is nice if you're in the city for the first time!