Nicolas's communication was great. Directions from the airport were spot on, although we had a slight issue in finding the exact apartment (the correct buzzer is 3rd down left side; apartment is on the 5th floor). The apartment itself was very nice...older and a little on the funky side but clean and well-equipped for our stay. We loved the balcony and the surprise bottle of wine!
We also really enjoyed the neighborhood -- lively and fun with many restaurants just down the street. It's only a couple of blocks to a main drag where you can catch a taxi or public transportation (although we walked pretty much everywhere we went in Barcelona). With the balcony doors closed at night, street noise was never an issue. Wifi and AC worked well the whole time we were there.
One thing that would have been nice was instructions for the washing machine. We ran one load fine but the second load was on some endless cycle of rinse and spin, rinse and spin...not sure what setting we hit to make that happen!
I would definitely recommend Nicolas's apartment as a great home base for your Barcelona visit (provided you are fine with climbing five flights of stairs to get there).