We were three and stayed for 6 nights at Cristina&Marta's place. Cristina responded to all our messages in time so it was easy to reach out to her for everything we needed. We were warmly welcomed by Cristina with bottle of wine and she had clearly+carefully laid out all the practical instructions we would need to get started. The apartment was secured with devices and alarms (something you will appreciate after spending few days in Spain). Apartment was clean, enough "clean" towels were provided which I am happy about. It was also quite roomy and came with all mentioned amenities.
You could hear the Vehicles passing by the apartments (mostly empty streets ) or any loud noise from outside and also if someone is loud in corridors. It didn't bother us but just a note to some one who is sensitive to noise.
If you are going to travel by metro, then you can easily walk to two nearby train stations, red line and blue line. Car parking is 400 meters straight line walk but it is paid one (8€ per day). We used both 5 day Barcelona metro card for local city commuting and a 2 day car park for day trips. It was convenient but the street outside the apartment is narrow so if you plan to stop the car to load/unload etc. then you would block the street. We never got the car right outside the apartment but always walked to-from the parking. Nearby streets are also narrow and many one-way lanes so keep gps navigation handy.
Overall, I had great time and I could safely recommend this place to my friends.