We, a group of 3 adults and 3 children, had a very pleasant stay in Jordi's apartment.
The location, in the fabulous barrio of Gràcia, is pretty much perfect; it's a bit away from the hustle and bustle, but still close enough to visit many key sites on foot.
Or by public transport if you so wish, Plaça de Gal·la Placídia is very well connected to pretty much everywhere in Barcelona by bus, train or metro.
A very good local market and a decent supermarket are just around the corner and there are a bunch of good bakeries, fruterias etc. at the plaça. The plaça also has ping-pong tables, room for playing football etc and a playground for the smallest ones. Having a place like that in immediate vicinity is a big big bonus when travelling with kids.
The apartment has good air-con and wi-fi, too.