I stayed in javiers apartment for 2 months, i had a very good time! the apartment is clean and nice. Javier is a very nice host, one time i left my key inside the apartment and in the lock. javier organized everything so that mechanics came and opened the door for me and exchanged the lock within 1 hour! the location of the apartment is very central and you can reach (almost) everything in madrid by foot. it is a bit noisy during the night but in the 4th floor it is silent enough to sleep.
i can recommend this apartment and javier as a host :)