I stayed with Pep for two weeks and had a great experience!
First off, the neighborhood is really great. I've been to Barcelona before but not to Gràcia and it was really wonderful. Lots of narrow streets, plazas with open-air cafes, and tons of great restaurants and cafes (including some third wave places for coffee-lovers). The rest of the city is easy to access via train but I spent most of my free time in Gràcia because I loved it so much.
As for the apartment -- Pep is a really great host! I enjoyed our conversations although I'm kind of introverted and tended to spend most of my apartment time in my room. The room BTW is very nice. It's not huge, but the bed was very comfortable, there's plenty of storage space, it's clean and well-decorated, and there's a desk you can work at (the wifi worked reliably and was pretty fast). And there's a balcony that overlooks the street. Much nicer than my apartment at home...
The apartment was incredibly clean, the bathroom was spacious, and the kitchen was clean and had everything I needed for some basic cooking.
Overall, it was a really pleasant stay!