We had a great time in Madrid, and Catalina's place was a great place to explore the city from. It had a fantastic location, with many great shops, bars and bakeries nearby (the Santo Bakehouse nearby is brilliant).
The apartment was really quite spacious, with all the facilities you could want for cooking, cleaning and relaxing when you've had a long day exploring. I would say that it can get quite noisy being a street-level apartment, especially on the weekends. The daily bin collection is both a positive and a negative in this respect!
Overall, we do recommend this place, and we would return one day should we come back to Madrid!