Note you check-in in a different location than the BNB, so factor that into your time. Overall, we had an excellent stay here. The company was very nice and helpful, and the apartment is as it looks. It is nearby the main center, so everything is very walkable including metro stations. I also learned that it is apart from the "touristy" parts of Barcelona, in a good way. Right in the middle of the city but away from any tourist gimmicks. Near museums, cafes, shops, etc.
The apartment is great for 3-4 people, and has a washer if needed.