The place where we stayed 'La Rambla', I think is the most happening and lively place in Barcelona. And for me this has been the most important aspect for staying at this apartment.
We had everything in the area ranging from shopping complexes, food stalls, local bars, pizzerias to churches and even one UNESCO World Heritage site (Güell's Palace to be precise).
As for our host, Maria's as good a host as you would expect. And for the apartment, it's really a nice and quite place to spend the night. The only downside I can think of is the apartment's WiFi which regularly got disrupted and we had no internet for a while. Also, since we visited Barcelona in March, it was quite cold and we were really surprised with the inconsistency of hot water for bathing. It was one of the quickest bath I've taken until now :P
Nevertheless, the place 'La Rambla' with it's exhilarating atmosphere, be it day or night, should be a good enough reason to stay at Maria's.