Having any complains for an amazing holiday in Madrid is very hard, so I will try to be objective in describing Melvin's apartment.
I have been there for 8 nights with my family - three of us.
Apartment is situated at the beginning on the crazy Malasana district, just above Gran Via, so you have everything in just few minutes walk from there - supermarket, pubs, cafe bars, bakeries and most important, the most lovely Plaza de San Ildefonso. We did not use public transport at all because all interesting points are at most 30 minutes of walk from there.
You can explore the district whole day and never get bored, because it is always something happening there during the day. Nights are extraordinary - concerts with bands, parties with DJ on every corner with thousand people wandering by.
So, for location 10+
Apartment is not new, but it is big, very clean and well equipped, so you feel very comfortable. Just do not expect that you can open the windows, because they look at the shaft in the middle of the building. This was not a problem to us, because we used the apartment only to sleep overnight and did not spend so much time in it.
Mark for the comfort will be 8.
As a host Melvin is accurate and helpful. We did not have so much contact, but it is expected from good host - to be invisible but available in case of need :-)
Next time I come to Madrid, I will probably book the same apartment.