This is a beautifully curated space. You really feel like you're in a converted mechanic's workshop on a film set. Because you are. Most horizontal surfaces are covered in carefully-chosen antiques and vintage items that really add to the atmosphere. Which means, since you're probably traveling with luggage, that you're storing your clothes on the floor. Also there are no windows: Great if you're sleeping off a bender, not great if you have to be somewhere on time in the morning. There's a reasonably outfitted kitchen space for a few simple meals.
It's clean and quiet. Geert-Jan has put a lot of time, money, and creativity into making it a special experience. If you're packing light and looking for a quirky place to spend a night or two in Rotterdam, I recommend it.