Flavio's place is great! It's very centrally located in Barcelona, right off of La Rambla, and easy to get to all of the major sightseeing attractions. The space itself is well put together, and the beds were very comfortable. Flavio's friend did a great job of explaining us the features of the apartment, as well as showing us around the city on a map.
The only thing of note is that there are a lot of stairs! If you aren't comfortable climbing stairs, then this probably isn't the place for you.