We had a nice stay in this Airbnb over the New Year's holiday. The apartment is relatively spacious, light, and airy, with a big living room / bedroom combo and then a nice kitchen with attached dining room, and the bathroom and shower were bright and spacious. Clean and comfortably appointed.
As the other reviews noted, the apartment is a long walk up several narrow flights of stairs - not fun with a lot of luggage, or after a long day of walking around the city. I noticed that many reviews for Barcelona Airbnbs complained about the noise of the city, but we didn't have any problems with that, even on New Year's Eve. The apartment is high enough up that when the windows were closed we did not hear much street noise.
The neighborhood of Montjuic is a little gritty and "up and coming", but it was convenient. A 15 minute walk to Las Ramblas, or 5 min to the Paral-lel metro stop. Lots of good restaurants on the nearby Carrer des Blesa. The host provided a nice guide of local restaurants, which was appreciated.
I thought the apartment was expensive for what it was, but that could always be due to price hikes over the holidays. I'd stay here again, but I'd also investigate other options more centrally located.