The apartment is great, small but with everything you need in it. It's clean and brand new.
Be aware that the bed is not huge, therefore it's perfect for couples but we found it still doable for good friends.
Communication is great thru the Airbnb channel, they respond very quickly.
Location is super, only 4 minutes walk to the subway and there are supermarkets, bars, cafés and restaurants very close. Almost everything in the centre is within walking distance.
We would highly recommend it to you! Next time we visit Madrid we will surely come back here.