We stayed here for six nights during a conference in June 2012. The size of our double room was good, however the single rooms in which some colleagues stayed vary in size and some are tiny! Make sure you ask if you can have a bigger single room if you feel claustrophobic! We were also lucky to stay on a non-smoking floor (living in Australia I hadn't even considered the possibility of ending up on a smoking floor!). If you want to have a non-smoking room make sure you specify this as the smoking floors and rooms do not smell very pleasant! The views from the rooms are spectacular, no matter on which side you stay - you either have a view of the bay or the city.
The breakfast buffet was nice (not the hotel's fault that we were a bit over it after six days). The bar in the hotel also features spectacular views over the city, especially at night. Unfortunately it is quite pricey (even for Japan standards) and last call for drinks is at 9.30pm.