Carlos very nicely met part of our group a little earlier than the listed check-in time so they didn't have to wait around with all our luggage. I arrived a day later and didn't know the actual apartment number so couldn't buzz from the outside to be let in. A lady let me in and the details are inside in the lobby area - would be easier outside however so you can buzz straight to your apartment.
The apartment was very clean and a great size for 3 people, generous lounge area to relax in. You could easily have space away from people if you wanted. The bathroom was pretty small, and the shower was tiny, but for the amount of time you spend in there, it's not a big deal. All linens were clean and the beds comfy. I found it pretty quiet. And there was a bottle of bubbles for us in the fridge.
The neighborhood felt very safe, (even at night) and there was an amazing bakery straight downstairs and some great tapas restaurants and supermarkets within a 10 min walk. Sagrada Famíla was about a 10-15 min walk and next to a train station. We walked back from Park Güell which was about 30 min. €12-€15 seemed to be the cab price back to the apartment from a lot places - San train station, Las Rambla, Magic Fountain.
All in all, it was a great stay.