We stayed two nights and had a good time. We stayed comfortably with our son at 20 months - Julia had even prepared a cot for him. Julia was very friendly and helpful and even lent us a rain cover for our stroller (that she had someone bring over in the morning) as Madrid was hit by a major thunder storm when we were there. She was fast and easy to get a hold of - before and during our stay.
We walked a lot (despite the rain...) and the apartment felt a bit out of the way. However, it is close to several metro stops so it is easy to get around. We had a great time - thanks for having us!