I have been there with my family for a three days visit of Madrid.
The apartment itself is as per description: well equipped, well placed (we walked to all the major sites of the city center), renewed... and quiet.
Equipped of air conditioning so no worry if it is hot outside, to rest.
Igniacio has been very kind for the check-in (all was perfect), taking our luggages at the fourth floor with no elevator (as per description).
I personally did not like the district (it is grubby) and the building itself (it is an old building not well maintained). The windows of the flat are on internal court (which is good for quiet) in front of other windows very closed (but this is not Igniacio's fault).
No way to park the car in the district with very narrow streets: you have to go to car parking (@20€ per 24 hours).
Give Igniacio your plate number in advance if you go there with your private car as the city center access is controlled by traffic cameras.