We enjoyed our stay in David's appartment. The location is awesome as it's in the very heart of Madird and you can walk everywhere.
David is very responsive and helpful host, his instructions are easy to follow, check-in/out process is great.
The only minus that we could see is that the place is very small and there is no windows.
It's really great place to stay for 3-4 days, if you appreciate time and easiness to communicate with host.