Just stayed with a colleague at Park Montjuic for 8 nights and had a pleasant experience.
The apartment is exactly as shown in the pictures and is located in a nice quiet street, with lots of cafées and bars just a few minutes walk away. We walked to and from various sights and places in Barcelona which is quite easy from this location - eg The Rambla which is 10 minutes walk away and the harbour that is 15-20 minutes away.

Xavier is very informative and with his mails it's very easy to get to the apartment from the airport as well as finding the best tapasbars in the neighborhood.

Arrival and departure was very smooth, with the people meeting us being right on time and very pleasant.

I'll happily recommend this apartment to anyone travelling to Barcelona - we were just 2 but it can easily hold 6-8 persons.