I stayed in Susana's flat for my first visit to Barcelona - I couldn't have asked for a better experience!
The flat is immaculately clean and in a great location (very close to the Sagrada Familia); despite being in a touristy spot the the flat is incredibly quiet (it's in a peaceful side street, so no noise from the road!). It's very walkable everywhere, or you can jump on the underground literally around the corner.
I stayed in the flat by myself but it would be suitable for more people - I loved the outside terrace to soak up some sun.
The host, Susana, is lovely and super friendly - she'll go the extra mile to give you advice on activities / restaurants or anything else you may need (try the Churreria on the other side of the road!). thank you Susana!