Great location, just behind Plaça Reial, so all the convenience of being right in the heart of the Old Gothic District, but quiet. We walked almost everywhere, and with young children, we could also pop back for a rest when they got tired. The decor is basic but very functional: a decent kitchen, dishwasher, laundry room (all good to have when when travelling with children).
Klaus met us in the Placa in person for check-in to show us the apartment. He provides some good tips on tapas bars and restaurants. When we decided to cook ourselves, we bought everything from Carrefour market on La Rambla; it has everything you could possibly need (avoid the small supermarkets in the alleys around the apartment; they are not good value (even for bottled water).
We had a great time in Barcelona and would stay here again if we come back.