First time as a airbnb user, and now I will definitely check airbnb before hotels.
The apartment was great, clean and ideally located. Well equipped, with all you need (plenty of towels, Clim, etc... :)
Maps of the city and discount coupons, last but not least : a decent DSL connection ! :D
Our host Nuria was really kind and always there to help us. Nuria even checked metro frequency for us because we checked in on a holiday.
A basket of fruits as a welcome, what else? :)
Next time I go to Madrid, I first check if his flat is free :)