Others have talked a lot about the place so I'll be talking about something else.
The apartment has an unbeatable location. You are right in the center of everything yet it's very quiet in the night. Walking distance to everything. There are many great local restaurants and bars right on the street and in the neighborhood. (Make sure you don't miss the Two Schmucks downstairs. It's one of the best 50 bars in the world!
As for Rives, he is a wonderful host. Always willing to give you advice on travelling in the city. Had some nice talks in the evening. He will treat you like an old friend than simply a guest.
Overall it was a great stay. Looking forward to be back in Barcelona again.