After spending 10 days at Valerio's place I can fully recommend it to everyone.
to start with location - the perfect one. On the south side - few steps from super vibrant Gran Via with shopping and dinning options, few minutes away from Sol/Espana squares; on the northern side - Malasana with restaurants, bars and lovely squares... but still perfectly quite for light sleepers and safe, if you have concerns. It is well connected with other areas of interest - short walk to Prado area or subway to la Latina (although it is also nice 15 min walk, at most)
the apartments is well maintained and clean. Well designed with everything one can need. It has two separate bedrooms (both with a double bed) and large living area/kitchen. Space is well organized, with enough storage area. We were in Madrid during very cold days but heating was working well. Kitchen is well equipped, although we did not prepare food often... There are several supermarkets in the neighborhood, exclusive and regular one.