My three friends and I stayed in Siebe's place for 5 nights while we visited Amsterdam. His apartment is absolutely beautiful, it was nicer than any hotel I've ever stayed in. It had everything we needed (wifi, a fridge and cooker, even a television with channels) and the shower is amazing, it's like a tropical rain shower where the water comes from straight above.
The location is just outside the centre in a quiet residential street, so easy to reach the centre on bikes but still quiet and calm at night.
Siebe himself is an excellent host, he was very flexible with the check in even when we were delayed at the airport we messaged him and he arranged to meet us to hand over the keys and tell us about the apartment. He also left us a note on the dining table which had some tips on where to eat/go for drinks in the surrounding area which was lovely.
Altogether we really enjoyed our stay the apartment is a little bit of a squish with 4 people but the sofa bed is very big and comfortable so there was no fighting over the bedroom! Two people staying would have plenty of extra space, but definitely 4 people can stay comfortably also. My friends and I would all stay here again in a heartbeat.