I stayed at Jonathan's place for 4 weeks through Jan into early February. I had an extremely comfortable stay in the apartment. Lots of space in the room, amazing wifi, heating on in the morning and eve, good light throughout the day, everything you need in the kitchen and a good shower, as well as a memory foam mattress I slept very well on. Jonathan is easy to be around, gives you space to chill and cook, but is more than willing to chat and give you some tips for Madrid.
The location is also great. Embajadores is a 20 minute walk to Sol/Gran Via, 10 mins to Retiro and there's loads of places to shop, drink and eat close by.
Highly recommend and so would definitely rent again.
Ben