Fernando's place is a cozy small apartment right in the heart of Madrid (five minutes from metro station Tribunal which is connected straight-away with both the airport and some of Madrid's primary central spots, e.g. Sol, Gran Via, Atocha etc.). The area around it is quiet and residential and has several nice cafes, restaurants, and so on.
The apartment itself can accommodate a bunch of friends/ couples or a family rather nicely, but mostly for sleep, as it only has one room (plus a small bathroom). I think it's ideal for a low-budget but decent place to sleep/rest when not walking around the city.
On the downside, we did notice a few small-sized bugs, but to be honest we had prepared ourselves for worse after reading some of the comments here. Obviously Fernando has taken his measures against bugs and we did not encounter anything remotely unacceptable.
In truth, the host came a little late for the check-in (roughly half an hour) and the language barrier was a little restrictive, yet he was friendly, albeit in a reserved way, and graciously allowed us to check-out an hour later than we'd originally agreed upon (and in an ironic stroke of fate we too arrived a little late to get our things!).
All in all, Fernando's place is in a very convenient, yet simultaneously very quiet, central spot. If its full 5-person capacity is used, it seems ideal if you just need a good place to crash after spending a day walking around Madrid. If its booked by less people it'll definitely be significantly more comfortable.