The apartment is great, very cosy and nicely decorated with a lot of personality, unlike the majority of Airbnb apartments full of beige and white IKEA furniture...
All the amenities are available, from dished and spices in the kitchen to toiletries and hair-dryer in the bathroom. You can also enjoy a nice selection of art and travel books.
The heating system is efficient and the bed super comfortable. It is a real queen-size which is rare in Spain.
The location is great, very central in Madrid and walking distance from the main museums. Lavapiés offers a great mix of bars and restaurants too.
The only negative is that this area is pretty unsecure; there are some "suspicious" individuals on the street at night. A pickpocket robbed my wallet the first night. During the day it is 100% safe but I would advise to come back by taxi or Über at night.