We have sailed on HAL 3 times, twice on the Maasdam and on the old New Amsterdam (sister ship to the Noordam) which is no longer in service.
The Massdam is very accessible and our accessible cabin was very large and well equipped. Not all of HAL's accessible cabins are equally large. Check the cabin on the ship layout, they are pretty accurate.
We did have trouble with getting information from HAL's front office before we sailed, but aboard ship the service was great.