It's a good property if you are staying with some friends / family. Don't book if you have anyone that cannot get up to the fourth floor by stairs. It's innaccessable for anyone older or with disability. It warns you before booking anyway.
The property itself is as described and has a good view of the square. The location is pretty good as there are lots of things to see around you. It's about a 30 minute walk to the nearest beech.
The only issues we had with the property were the firm mattresses, thin pillows and somewhere to put your clothes in the bedrooms (there's a rack outside the bedroom). Also, the apartments are not very sound proof so consider that if you're a light sleeper. Other than that we had no complaints.
If you get to Barcelona early and need to leave your bags somewhere. They will allow you to leave them there after 11.00 am and venture off and come back at 15:00. You will have the keys at that point and your bags will be in your apartment. Make sure to/ organize this in advance as we had trouble getting through on the phone.