This is a good location to base yourself to explore Barcelona.
A few of the key attractions are pretty close. The flat is very close to a couple of Gaudi's famous works; Casa Milla & Batlló. La Rambla is a 15 minute walk and beyond that, the beach is a further 15 minutes.
The main train station, Barcelona Sants, is a 7 min taxi ride and the airport shuttle bus drops you a 10 minute walk away from the flat.
Sid was easy to contact on the day of arrival and we were shown into the apartment without fuss. The room was clean with towels provided and a fan which was essential on one evening! The bathroom was clean and towels were provided. There was a problem with the wi-fi on the first day, but as we were out most of the day it was not a problem, but Sid quickly fixed it.
I would recommend the apartment to anyone looking for a base to explore the city, who is happy to walk 15-20 minutes to some locations.