What a find! We had the Mondriaan Suite and the room was fantastic. Really big, even by North American standards, with lots of tasteful and thoughtful details I wouldn't think I could get at this price. It faces the gardens at the back of the building, so it was very quiet (until the birds woke up!). The staff was also so nice and very helpful. We didn't get breakfast, but they gave us voucher for 10% off at the cafe down the street every morning, which was great. The location really can't be beat. Walking distance to the museums, right on the 2 tram line so you can get anywhere you need to go in a snap, but in a quiet residential area.
My one big drawback for the room relates to my 2 stars for sleep quality. The bed in the room is really two twin bed shoved together. That's pretty standard in Europe, but in this one there's actually a few inches of a gap between the mattresses and they were made up with separate bedding. It was rather awkward. Also, being on the top floor and with the warm weather, it got really stuffy in the room. Throw in some jetlag on top of that and it made for rough sleeping. It wasn't so bad that I regret staying here, though, and I would stay here again in a heartbeat.