First with the best - the location is very nice. The apartment is located in Lavapies - a very colorful neighborhood very close to the main attractions of the city. We didn't actually need the subway much. There are some very nice bars and little restaurants right next to the the apartment. I really liked the atmosphere of the area. I tried some of the bars and restaurants around Lavapies subway station and they were really good at affordable prices (compared to the more tourist areas). There is a 24/7 super market nearby.
The apartment itself is on the ground floor with windows up high, facing an interior yard, so it's not very lighted but I guess that in summer this would be good. It is a one room space turned into a studio, with something like a gallery for sleeping. The gallery is about 160 cm high. I had no problems with that. The bathroom is separated by a thin wall - I had no problem with that either, but I didn't care so much for privacy. The studio is very nicely decorated and the kitchen is fully furnished.
I had wonderful time in Madrid and at Ma Victoria's place. Definitely worth it.