Eduardo's place is beautiful styled and unique, with artwork everywhere and lots of welcoming touches. There were fresh pastries every morning, and an excellent espresso machine to make coffee.
The location was absolutely perfect - very close to centre, Plaza Mayor, and all kinds of good places to eat and drink. It was easy to walk to everywhere we wanted to go, from Malasaña, Lavapies, Chueca, Museo Del Prado and Reina Sofia. There is even an amazing Vegan restaurant right next door that we ate at twice it was so good.
The room was beautiful and cozy, though with it being underground the damp and dark can be a little intense. Eduardo does warn in the add that there are no windows; so it was exactly as described and I can't complain, but it did make waking up in the morning a little challenging, so if you're sensitive about light, make sure you take that into consideration.
As for the damp, Eduardo has gone to great lengths to keep it to a minimum, with fans and a dehumidifier, which both help a great deal, but it is still something you notice.
Everything else about the flat more than made up for these things, but I think it is worth mentioning them.