Me and my girlfriend spent one week at Martin's apartment and had a great time. Martin is a great host who knows everything about the neighbourhood and gave us good tips on e.g. free parking, where to eat and which beach to go. We asked for an early check-in, which Martin did without problems or extra fees.
The apartment itself is nice and very well located. It's on the third floor an Martin lives on the first floor. There are no extra doors after the stairs so you hear if someone is walking around the house, but this rarely happened.
Martin provides pots and pans for cooking so you can cook there. However, the table is a bit small so you might not be able to place all of your meal there.
You can explore most things in Den Haag by foot starting at the apartment, we only used the tram to go to the beach.
I would surely recommend Martin's apartment!