We were 3 friends and spent 4 nights and overall our stay was passable. The apartment is in a nice position. It's in a quiet area, it's close to many shops and you can easily get to any destination with the metro.
There is a lovely view from both balconies. Self check in was easy. We got there earlier than the check in time (around 12) to drop our bags and met the cleaning lady, who was very kind and helpful (she briefed us about the house). The A/C worked well and was a life saver.
If you choose to stay in this accomodation though, you must note that there are no essentials in the kitchen (no salt, sugar, oil etc) and the host only provides 2 rolls of toilet paper (which is not really much if you are 3 people staying for a few days) and he would not give extra ones if you run out! (Yes, it is all stated in the list of rules and regulations, but I think these are worth mentioning, since there is no flexibility on the rules).
On a side note, we tried watching the TV and it wasn't working. When we contacted the host about this issue he quickly sent someone to work on it. The TV is a bit old though and we still couldn't watch majority of the channels.
Unfortunately, I have to say there was a bad odour that came in every morning and every evening from the kitchen balcony (like sewer). We couldn't really detect what it was, but it was really disturbing.
In conclusion, I'd say the apartment is decent, works well if you're just looking for a place where to rest your head during your stay in Barcelona.