Overall it was a good experience, the airbnb is very well located in the heart of Madrid, perfect for a city trip! The apt. has (almost) everything you need, it is very cozy and modern. Also the check-in is very easy to do.
However, the communication with the host was rather bad. We asked several things to which we never got an answer, instead we received a very unpersonal standard message.
In the description we saw that the airbnb is equipped with an oven, which was important for us, however there was none. A further negative point was that the warm water in the shower works only for about 15min, then you have to wait again for the warm water.
Also the street next to the apt. is quite noisy but we knew that already, so just buy some ear plugs and you'll be fine. ;)