My stay at Casa Cosi was fine. The place was very clean, and the terrace is nice, but inside the apartment is a bit dark and the bathroom is not renovated. It feels like a mediocre apartment that has been dressed up with fun decorations. Overall its a fine place, but felt overpriced and there is a lack of feeling of genuine hospitality with the lack of amenities and nice touches which are usually provided in an airbnb of this price range. I will add, though, that the woman who checked me in was readily available via whatsapp and accommodated a late check out for me.
The surrounding blocks are also interesting as they seem both sleepy culture wise and loud with street sounds. Easy walk to the Sagrada Familia.