I have been in Madrid with two friends for a long weekend. The flat is great and centrally located giving access to plenty of shops, bars and restaurants.
Communication with the owner has been smooth. The flat was clean and according to the pictures on the ad.
The only thing to mention is that the master bedroom doesn't have a main door so there is some lack in privacy and if you are sharing the flat with other people as we did, it wasn't ideal. Also the air conditioning is just in the living, no air conditioning in the bedrooms, which is something to consider when you have 35 degreed outside!
Overall we had a good experience.