Joaquin was a great host meeting at the apartment and showing us everything that needed to be shown. The apartment itself was excellent, but you should be aware that the bedrooms didn't have much in the way of direct sunlight so you'll need an alarm clock to wake you up on time. If you leave the master bedroom window open to get cross-ventilation you might be hearing a lot of your neighbors. (There was also a small problem with the shower that I'm sure he's fixed :). On the other hand the living room has a wonderfully comfortable couch and is bright and airy.
The location is excellent with the Metro and what seemed to us to be the best parts of Barcelona within easy walking distance (but remember we're just visitors so what do we know). Overall Barcelona was a great experience and his apartment added to it!