We stayed here with our two children (9 & 5). The Gracia neighbourhood feels really safe and quiet and we were really pleased that we chose this over the Gothic Quarter, which was more of a tourist trap.
The apartment itself is relatively small but has super high ceilings, so it doesn't feel cramped and everything was really clean. It felt like a stylish place to stay in a great area. We felt very at home there.
One thing to consider if you have children is that children's room is just a dividing wall, meaning noise travels easily between there and the main room of the apartment. We were so tired from exploring the city each day, that we went to bed at the same time as the kids but if you have plans to stay up late, this might be an issue.
We bought the Hola Barcelona card, which gives you unlimited travel by metro and bus. The metro was nearby and really easy to use and made getting around the city really easy from this apartment.
Margot's communication was really excellent and she helped us book a taxi to the airport on our way home.
I would highly recommend this place if you're visiting Barcelona.
Thanks again, Margot.