I stayed in this apartment for 6 nights this August. My boyfriend and I absolutely loved it - although it is small it actually seems bigger than the pictures suggest and it is perfect for a break of any length in Barcelona. The location is also brilliant - the El Raval district that it is in is full of lovely little restaurants and wine bars and you can definitely escape from other tourists! It is also only a 10/15 minute walk from la Ramblas and is close to two metro stations that serve most metro lines for the rest of the city. The building is quiet and the terrace (a big highlight) seems very private. There were no problems at all with the facilities and the checking in and out was very smooth - we were even able to check out a little later.
We were booked into a hotel for our last two nights (arranged beforehand) and we were even a little nervous that it wouldn't be as nice as this apartment! I would really recommend it - especially to a couple. Loved it!