I came to Barcelona a week ago with a couple of friends. We had a lovely stay at Casa Tortilla and Fabiana and Marcello were great hosts.
As for location, the house is very close to Sagrada Familia (Catherdral & Metro :D ) - just a 3 min walk, and a few metro stations away from Las Ramblas (where you would probably want to shop &party)
The apt has everything you might need and Fab was so kind and waited us at night when we arrived with a bottle of Spanish red wine and of course, tortilla :)
The house is very clean and everything is new and tastefully arranged. Nevertheless, it is pretty small (thou in pictures it looks larger). This was not a problem for us, as we were six friends and didn't spent much time indoors.
The flat is very distinctive from any buildings around and it has a special feeling of story & fantasy. There are a lot of plants and the air in the morning is great.
The kitchen is very well equipped and you can cook anything you like (their markets are great, btw)
Neighbours seemed to be seniors, so you shouldn't be too loud. especially at night.
Not so great stuff for us:
- if you need wireless, there is connection but the signal is kind of slow (works just fine for emails and basic stuff)
- the flat in no smoking and if you are smoker you have to go outside

All in all, we had a lovely stay and I would recommend Fabiana as a very trustworthy, prompt and kind host. I would stay here again if I visit Barcelona and also will recommend it to my friends and family.