AMAZING!
I stayed one week in the apartment with a friend and we couldn't have been happier :). Everything from booking, over check in to check out worked without problem. The apartment was spotless clean and it has everything you need to feel at home. We really appreciated the location: you're within walking distance from the beach and you have a metro line basically just around the corner to take you to other parts of the city. It is very nice to not stay in the most touristy parts of the Barcelona because you can enjoy the calmness after a day exploring the city.
I literally have nothing negative to say about this place - I can recommend everyone to stay here. When you do, don't forget to explore some of the restaurants in the area. Roger has left some very useful recommendations that shouldn't be missed!