Paula and her husband are a lovely couple and they were very nice to deal with. The apartment is in a fantastic location, especially if you are interested in the museums (Prado, Reina Sofía, Thuyssen) and the Parque del Buen Retiro. You are practically next door!
The apartment is a studio on the second floor (in US terminology) with a pretty well-equipped kitchen and would serve well for either short or longer stays.
Our only issue for us was the hot water. It ran out after one shower and so the second person had to use cold water. I hope they can take care of that because otherwise the place was great.