Yes, the rooms are not large. Yes, the bathroom needs updating and is TINY (the property is very old but remodeled...whadaya gonna do?) But the rooms themselves are smartly appointed for business. The bed is very comfortable. That's 90% of the business battle there. The decor is also modern throughout. The lobby, champagne bar, and restaurants really are very beautiful and well designed. If you have a problem with the public spaces, then you must be an incredibly hard to please person. They're superb. The rooms, hallways, and common areas are all very clean as well, as you would expect at a 4 star property in Japan.
Also the service is very good. The PBX is quick, efficient, and responsive. Rooms service sometimes had issues with English but someone would always come online to help translate. I ate the after midnight room service twice and would not advise. Not good either time, but the restaurants all looked nice and the after midnight selectiosn aren't on any of the restaurant menus. So there is that.
I think where some of the negativity comes from is that we often get so spoiled with 5 star hotels in Asia. Or one sometimes expects 5 stars out of an Intercontinental property. This is not a 5 star hotel. On some websites it is listed as a 5 star property and on some websites as a 4 or 4.5 star property. I would completely agree with the assessment that it is not a 5 star property. But it is a very good 4 star property in a very good neighborhood. Think: good Marriott property and less Four Seasons/Ritz-Carlton and you'll have perfectly set expectations.