Booked two rooms for my family of four, for a one-night stopover after the ferry journey, before driving further south.
The hotel is in a perfect location within the walls of the old city, and the relatively high price reflects this. Our 3rd floor rooms, served by an elevator, were clean (if a bit musty), comfortable and quiet.
The receptionist was very helpful and friendly (as usual, in France, an attempt at a few words of French, however basic, takes you a long way), and did her best to explain parking arrangements. The hotel have a pre-paid overnight rate for the car-parks outside the city walls, which we couldn't quite make work for us (our pre-paid ticket did not get us out of the car-park, and the car-park attendant was not at all helpful), so we just paid the standard rate of 12 Euros to exit in the morning - a minor inconvenience which you can probably avoid if you have a better command of the language.
The many shops, restaurants and bars of the Intra Muros are just a short walk away from the hotel, and, to soak up the charm of St. Malo for just one night, we were happy to pay the money and give ourselves a treat.