David is the best! We really couldn't ask for someone better.
First - the apartment: It's grate (we were 4 people). It was clean, tidy, well equipped with quality products. It has great air conditioning (something that is really missing in Spain). It has two spacious bedrooms, many closets, well equipped kitchen, one big bathroom and another small one and a lovely living room. It's located about 6-7 minutes (walking) from the main Sants station and you can really get anywhere from there. Very quite place with everything you need close by. There were treats when we came to the apartment (some drinks in the fridge, and some cookies).
Second - David. As we said - we really couldn't ask for someone better.
David helped us getting our suitcases to the apartment, helped us locate a cheap parking location, gave an informative and detailed guidance on how to operate the electric equipment (like how to switch the television sound track to English (very important! :-) )).
David also helped us with some problems that we had no other way of solving, way over then we could ever ask. He helped us print some tickets we forgot at home, assisted us with traveling arrangements to the air port (I broke my leg before the trip and I used a wheel-chair and we couldn't get the suitcases to the airport without that help). He was always available and always happy to help without never giving the impression that we are some kind of a burden (although we know we kind of were...).
We will defiantly try to get this apartment on the next time we'll be in Barcelona.
There is only one way of saying it: If you need a place in Barcelona and this apartment is available - get it! You'll thank me (and David) later!