We just spent 5 nights here and thoroughly enjoyed our stay.
The staff were friendly and engaging, the room was very comfortable and the location is great.
Our room (15) had a very comfortable bed, nice furnishings, quality linens and the bathroom amenities were very nice.
Our only complaint with the room was the automatic lighting in the toilet (motion activated), if you get up to use the bathroom in the night, the light will automatically turn on and wake your companion up, you can't deactivate it. Big design mistake!!!!
The breakfast was very enjoyable, especially if the weather lets you sit outside. Our only complaint was that breakfast isn't served until 8.00am, if you want to get an early start you won't be able to get breakfast.
I visit Rotterdam 3-4 times a year for business and over the years have stayed at pretty much all of the better hotels in town, Morgan and Mees is a much needed addition to the city.
All in all, we'd definitely recommend a stay at Morgan and Mees.