Carina's place is of awesome value. The location is very easy for moving around. 5 minute walk from the apartment there is a metro stop which takes you directly to the city center and beach. There is a nice bakery near the apartment (just behind the bus stop in the east) and quite large supermarket in the west considering the usual size of these street supermarkets. Park Güell is within walking distance (30 min/2 km) and so is Sant Pau hospital (architecture value).
The rooms itself are well organized. For some it will feel a bit cramped but most likely you aren't in BCN to enjoy the indoors.
On the other hand, there was shampoo, towels, coffee and even a large bottle of water in the freezer. There are extra blankets for you to use, city maps in a basket (we left one extra) and a good air conditioning in the room.
A special mention needs to be made of Carina's hospitality. She and her husband Pablo are very friendly and eager to share local know-how. Prepare a pencil and a paper when you ask her for tips.
Carina is specially handy if the intention of your BCN visit is to dive into architecture as she is an architect herself and can give quite nice recommendations for sights that you won't really know to look for from anywhere else.
We stayed for 3 nights and we would come back without hesitation.