Our stay in Diana's studio can be described as "functional" or "ok" It is situated in a very cool neighborhood (malasaña) and very close to metro and rail stations. The positives: location and functionality. the negatives: it's on a pretty steep 4th floor walk up with no-so sturdy stairs. - it is a very old building in an old city so it's to be expected but the stairs were tricky to walk up and down especially with large suitcases (we are in Europe for two weeks) The biggest problem for me was the entrance and temperature of the studio. I am close to 6ft tall and the entrance is no bigger than 4ft so that meant I had to squat down every day to enter and exit the space. Very uncomfortable and quite honestly... should be addressed. The studio was clean and tidy. Included a comfortable bed (pillows were terrible though) microwave, washing machine, tabletop stove, small flat-screen tv and enough clothing storage for two. Bathroom is very small but functional. The shower is pretty tight and my girlfriend mentioned she could barely bend down to shave her legs, so keep that in mind. My main gripe of the bathroom was the hot water heater. Though we were given a heads up by our host that the hot water did run out after a certain period... We weren't expecting not to be able to shower in hot water if one of us took longer than 5-8 minutes. Every night one of us took a tepid shower and it was kind of a bummer because.... The apartment is an icebox. Weather in Madrid for our stay was around 50-65 degrees(f) so we understood it would be somewhat cold... However it's drafty and very cold. We were supplied with a small space heater which didn't really do the trick so we had to sleep with sweats on. We're from NYC - we know cold weather so it's not like we haven't experienced this before but still should be noted for future visitors.
Our host Diana was nice and helpful (ordered us a taxi for our flight to London) she did give us some basic tips for our travels along with a guide for the city and a map.
Overall I would categorize this listing as a slightly above average due to its functionality and location. However if you're a tall guy or gal - consider other options.