Location was very good, just next to Gran Via. Communication with host was also on a good level + we got extra breakfast!
What I find difficult is space - this is 9 people apartment, quite pricy but there is no space and lack of windows (only 4 windows with no view at all. One room is without windows). We got only 1 key for 9 people .. I think standard should be at least 2 for such big group. What is more, interior is cheap and broken - we had to call from day 1 to fix night lamps (2 out of 3 were not working) and wardrobe was without possibility to hang clothes (no racks).
I would say this is ok to stay if you plan to spent all day sightseeing Madrid and only sleep there.