Javier's apartment is just as described, while it's not huge; it's perfect for one or two people. The bed is comfortable (actually two twin beds pushed together, but I used a luggage strap around the legs to keep them from sliding apart), the shower is hot, with good pressure, and the place was a comfortable temperature. I know he mentions a couple of times in his review that the soundproof windows cut down on the noise, and I want to reiterate that it's absolutely true. At the times that we had the windows open, we could hear a lot of noise; but once they were shut, the only thing that could penetrate them were sirens.
The apartment has a microwave, cooktop, refrigerator sink and toaster, as well as a carafe to heat water for coffee or tea, and a hairdryer in the bathroom. The only things that I would have liked would have been to be able to lock the door from the inside without the key. If one of us went out and the other stayed behind, our only options would be to lock the other inside or leave the door unlocked; we chose to leave it unlocked as there were other locked doors between the street and the apartment.
Javier was very friendly when we met him to get the keys, and told us where the local markets were; one about a block away, and a 24 hour one about a .5km walk. He let us know that he would be available 24 hours a day for us, but everything went smoothly, so we didn't need to contact him.
The apartment is very well situated, very close to Museo Reina Sofia, about a 4 to 5 minute walk to Metro Estación del Arte, and about 10 minutes from Atocha.
I'd definitely stay at Javier's place again