The rooms is a bit better than it looks on the photos. The apartment has 2 rooms, one if this, one for other guests, so you share bathroom and kitchen with just one another room, not 5 or 10 as it is sometimes) The walls in the apartment are not too thick, so you can hear neighbors a bit. It wasn't an issue for me, no loud neighbors, and I think it's the same for all Barcelona city center, that's just how they builded houses. But any case, if you a light sleeper, keep it in might.
We only staid in this room for three nights, but I think it has everything for a long stay to be comfortable too - there is a table to work in the room, and as I said kitchen and bathroom just for 2 rooms. Small entering hall with a small sofa, and everything looks very night. The bed in the room is very comfortable, everything was clean.
The location is good. The street with the house itself is narrow and not so central, but it takes just 5-10 minutes to get to the most touristic places.