The location is really, really great for exploring Madrid and communication with the host was relatively fast and always available. Check-in and check-out were no problem.
The place itself is apparently part of a former larger apartment that was turned into multiple small apartments. Consequently it is quite dark (few windows only to dim and small courtyards) and relatively cramped. It’s also not exactly super-quiet (AC hum of other apartments being the main issue), though I imagine if there were windows out front it would be quite a bit louder. Everything in the apartment is quite used up: the shower is leaky, the sleeping sofa is long past it’s due, everything looks like it was used a thousand times and never replaced.
For exploring the city this place is great. For actually being in the place and also enjoying your time there it’s not so great.