I traveled together with two of my colleagues to attend a conference held in IFEMA. Javier's apartment was perfect for this purpose as it is only 3 metro stations away from IFEMA and 4 from airport.
Apartment was super clean and tidy, communication and check-in went flawless. Javier was amazing host, very friendly and gave us a lot of useful tips, from getting around neighbourhood and local shops, restaurants and metro system to touristic tips about Madrid... Metro is really well organised and easy to get accustomed. So if you want to do some sightseeing you will need around 30-40 minutes to reach any famous Madrid tourist attraction.
I would highly recommend Javier's place and will book again if I have a chance to travel to Madrid in the future!