It was our first time in Barcelona and the apartment was amazing. There was a rooftop balcony where we were able to watch the sunrise and relax under the stars with a glad of sangria on hand. In order to access the roof, you need to go up a narrow spiral staircase. The apartment was very spacious and clean. The whole place felt very homey.
The subway is a 4 minute walk and the bus is two blocks away. My companion and I walked everywhere, but if you want to take public transportation I recommend getting a T-10 pass. The apartment is very central to all the local attractions. Sagrada Familia is 9 minutes east, park guell is 25 minutes north, cathedral is 33 minutes south from the apartment. There's no direct metro to take you to park guell, but if you take the v-19 bus, it literally takes you from the apartment to the park. The bus stop is only two blocks away. Also visit the bunker, it's on old military bunker that has a 360 degree view of Barcelona.
The bed was a bit stiff, but my companion was fine with it. The walls are thin so you might hear your neighbors talk occasionally. There's a lot of restaurants nearby and a convenient store a block away. Will definitely stay again if I were to revisit Barcelona.