David's place was excellent. It is situated in a great neighborhood (La Latina) and it is just a short walk from a metro station. David's done a great job with making sure the place is well furnished.
Madrid can be extremely hot during summer, which it happened to be during our stay. So we found the air conditioning to be absolutely vital. It's also worth mentioning, as others already have, that David's building lacks an elevator. It wasn't a problem for us to get our luggage up a few flights of stairs but those who have mobility issues may wish to bear this in mind.
Check-in at the place was a breeze. David had someone meet us there and was very accommodating when our flight to Madrid experienced massive delays. It would have been great to meet David in person but otherwise we are happy to have stayed there.