We had a great stay in Barcelona at Sonia's place. The location was really great for walking. We were about 15 minutes from Plaça de Catalunya which is where our tours met and the Aerobus has a stop (recommend if you're coming from the airport). Also, there's a nice grocery store literally right next door to the apartment. It's not open as late as some other stores around the city, but really convenient. We walked everywhere, and the apartment seemed to be a very central point from most of the attractions to see (Sagrada Familia, Gaudi's houses, Plaça de Catalunya, Arc de Triomf, etc.). It was about a 15-minute walk to these places which was perfect.
It was a little small, but perfect for the two of us. The main room is plenty big, but the kitchen and bathroom are really only for one person (no big deal). The apartment was clean and had everything you need. It's an older apartment complex and room, but it's been updated in places and so it doesn't feel outdated. It had a large window to keep it bright during the day.
Overall, I would definitely recommend this apartment and would definitely stay here again. :)