The apartment is very close to the Sagrada Familia and more importantly the metro station, which was very handy and we liked a lot. Apart from the Sagrada Familia however you almost always had to use the subway/metro to get to other nice spots in the city (beach for example is about 20-30 minutes with the subway). There is a supermarket nearby and also a little market.
We were with 7 people and there are only 6 real beds available, with the couch making another bed for 2 persons: not very handy to transform it from a couch into a bed each morning and evening, but doable. There are ventilators available in each room and you really do need them. If you sleep on the couch (like me) and the windows are open there is a lot of noise coming from the traffic.
Bed linnen and towels were available, which was nice. However there was only one towel per person, which was not sufficient for the whole week.
There is a small balcony, but trees cover the vision to the Sagrada.
A big plus is the WiFi-network (but not enough reach for the bedroom furthest away). I don't want to be nit picking or sound too negative, but this were the things we came to notice during our stay and it can only help others;)
Overall we liked our stay and had a great time:) Barcelona is a great city to visit and I would recommend this apartment to others.