Our stay was perfect. The apartement is spacious, clean, well equiped and really confortable.
We met only Rogier but it's a really nice person, very accommodating and he advised us on what to do and what to avoid depending of what kind of thing we wanted to do, he was really helpful !
The location of the appartement is perfect, at 5 mn on car of the ferry openair parking (12€ per 24hour, cheaper than public transport when you're more than 3) and the ferry is free to go to center of Amsterdam.
I recommend Nicole and Rogier apartment, you'll not regret it ;)