Fantastic! This apartment is in an excellent location in El Born which is such a great neighbourhood - very interesting and truly Spanish, rather than being overly touristy or fake (yet still has tourist shops and English-menus in restaurants). We have stayed in this neighbourhood before and know it can be noisy at night... And yes with the lovely big door/window open you can hear some noise - mostly chatter and occasional rubbish collectors. However, as soon as you shut the door, it is so peaceful and quiet.
We were also there when Barcelona was unbearably hot and the apartment was a saving grace - we went back so often during the day (due to its excellent location) and just hung out and had a siesta under the fans.
Having your own private lounge room was another excellent bonus which we really enjoyed utilising to have a siesta or a pre-dinner drink.
Extras - We were also given a great recommendation to get paella at Bogatell Beach and got to use their washing machine - thank goodness!
Overall, we had a fantastic trip and wouldn't hesitate to recommend this place - we will definitely return!