I had a great time staying at Casa Cosi! I stayed for five weeks in July and August 2021.
The apartment is very well laid out, and the queen-sized beds are very comfortable. The kitchen has all of your needs, including washer/ dryer, silverware, pots and pans, etc.
The apartment is in a great location, just a quick 10 minute walk to Gràcia. It is close to many shops, restaurants, grocery stores, and bars. It is also close to many lines of public transit. Overall the area is relatively quiet, which is nice for a long stay.
The host was very responsive to all of my questions and overall made the stay really easy. Would definitely stay again!