We found Alex and his team to be exceptionally accommodating with check in and check out, and answered all emails almost immediately. It was well stocked-they provided shampoo and laundry detergent which is always helpful to not have to purchase when traveling. Kitchen is basic-if you plan to cook full meals, it might be tough, but we found it fine for heating up pizza and basic needs.
The apartment was a good size for our family of 5, very utilitarian, and had a cute balcony overlooking the Parc de l'Espanya Industrial and Barcelona - Sants station. 5 minute walk from the train, metro, or bus. 10 minute walk to Placa d'Espanya. Anything else you want to see is easily reached by bus or metro. The system is very easy to use, and Alex provided me with all the details of how to get to and from the airport, and how to get around. There are restaurants, cafes and a nice, large grocery store, right across the street.
The only downside I would have to say, especially in August, was the lack of AC. With fans, and open windows you do get a nice breeze, but with temps being above 90f each day, it was VERY hot for sleeping. Small kids would be uncomfortable if not used to the heat.
If you are looking to be in the center of everything, this might not be the best location, but if you don't mind a 5-10 minute bus or metro ride, its a great, affordable place.