The hotel room itself was good enough. Nothing in perticular to put the finger on. The check-in was also satisfying.
However, there are some issues people should know before they arrive: The check in is at the start of the street, and is combined with a couple of other hotels at Mont Saint-Michel. If you go to the restaurant up the street, as pictured at hotels.com, you'll be sent back down again.
Check-in is not until 16 o'clock, so you'll have to kill some time in the VERY busy and narrow streets. We found some restaurants and had some drinks while waiting 4 hours with our backpacks.
The restaurant owned by the hotel closed at 16, but we found another to eat in the evening. The breakfast was in a restaurant across the street from the annex we stayed at.
Be sure to bring ear plugs, as the restaurants/shops starts restocking goods and preparing for the upcoming day before 7 in the morning.
Be aware that the whole town is flooded with tourists all day, but is almost dead after 17 o'clock. No street lights, and most shops closed. Only some restaurants are open (until 21). Then it's good night.