We and 11 of my friends stayed for 3 nights and it was perfect!
Just 2 blocks away from the beautiful Sagrada Familia, it is very easy to get anywhere in the city thanks to the different metro lines you can get directly from the Sagrada Familia.
The flat is spacious, everybody had a nice place to sleep, and for the price, I don't think there is a lot of competition.
To resume, if you want to gather with some friends for a nice week end in Barcelona, it is a perfect place.
Thanks to Nick :-)