Soraya is a wonderful host - flexible with arrival times, amazing suggestions list and terrific local advice. The apartment location is terrific, right in the cool part of madrid and within walking distance to come of Soraya's coolest suggestions (check out the markets, and please, please eat at La Mucca).
The only downside is the noise at night. Spain is a nighttime country, so if you're in bed before midnight, expect street noise. If you're a light sleeper, earplugs will help.