We stayed in Ester's place for a week and really enjoyed our time there. Ezio was helpful in getting us checked in (and helping us store luggage in the apartment a bit earlier) and explaining the neighborhood to us. There is a convenient (but not shown on Google Maps) subway entrance VERY close to the apartment. There are also some nicely placed escalators to access the shops, cafes, bars, etc. on top of the hills (the neighborhood has some nice hills). It was very straightforward and easy to get a taxi with the Cabify app to/from the apartment.
The apartment itself is wonderfully styled and decorated. The bedroom is nice and sunny in the morning. The furniture is a tasteful combination of antique and modern pieces. The front terrace is perfect for morning coffee and hanging out and reading. The Nespresso machine was really handy to have - you can buy capsules for it very inexpensively at the bonArea supermarket. The shower is especially nice - great water pressure and very hot (use the hand-held shower rather than the overhead).
The neighborhood is more like living like a local than as a tourist, which we enjoyed. It's very quiet at night and there are some good local restaurants around. Parc Guell is a short walk away and is a nice place to go for a walk/hike/run and explore some Gaudi architecture.
To conclude, we had a very positive experience and recommend Ester's place highly. :)