My one-week stay in Barcelona in the end of September 2012 was really nice!
I booked the apartment via airbnb for the first time and this has definitely been a good experience!
I was warmly welcomed by Eberhard, who is vey friendly and helpful. His apatment looks just the same as on the photos, it is very clean and comfortable, quite well equipped also. The old wooden windows and doors are just amazing! You can hear the neighbours talking loud sometimes, but this is very common for Barcelona, I believe.
The location is convenient - there is a short walk not only to St.Antoni, but also to green line Poble Sec and Paral.lel stations as well as to Avinguda del Paral.lel street with plenty of buses.
There are also two really cute cafes to have breakfast just nearby - Federal and Taranna (not sure abt the spelling).
Overall impression - very good, I would recommend renting this flat.