Perfect location - just as advertised. Carolina's friend, Alex, was very helpful in letting me into the apartment early. I did not meet Carolina in person, but in messages she was very informative. I visited during an unusually cold week in Barcelona, so inside the apartment was very cold when I arrived, but there is a heater in the bedroom that solved the problem. There is also an air conditioning unit in the living room/kitchen area which I imagine would be helpful during hotter months.
The apartment was nicely furnished and the kitchen was stocked with water bottles. I did not spend much time inside the apartment itself because the location was fantastically close to a Metro stop (2 min walking) and walking distance to La Rambla (10 min), shops, and good restaurants/bars in the immediate vicinity. It was also very easy to pick up a taxi when it was time for me to head to the airport.
It wasn't a problem for me since I came with only a small suitcase and backpack, but the narrow stairs coming up to the apartment could be troublesome for someone with a lot of luggage or large/heavy bags.
I noticed some street noise in the living room area, but none from the bedroom, which made for a quiet night of sleep.