This place is fantastic value, especially compared to the price of hotels in Barcelona. It's very close to the magic fountain and also about 5-10 minutes walk from Plaza Espanya, which makes it very easy to get to/from the airport (first stop on Aerobus A1) and also to Barcelona's very extensive metro system. It's also possible to walk everywhere if you have the energy.
The apartment itself is basic, in an older-style building, but a lot bigger than I was expecting. The living room is amply sized and there is a pretty decent kitchen too and coffee machine - very handy for making your own breakfast following a saunter through the markets the day before. (Or there's oodles of convenient stores and grocers very near the apartment).
The main downsides are a small shower, basically no natural light in the apartment, and some neighbours with noisy children - but these were really very minor issues. The whole point of visiting Barcelona is to spend time outside the apartment! There is a bar/restaurant in the same building, or if you want heaps of good food options, stroll down to Carrer de Blai :)
Finally, the hoist (Luis) was very helpful and replied to emails super quickly. His friend met me at the apartment and was very patient when I asked a long series of silly questions!
The bottom line: I would absolutely stay in this apartment again!