I stayed there two summers ago and agree with the report Robt760 wrote, except for a few details.

As a Diamond I had access to the RC, which is superb. Great food for breakfast, nice selection at dinner time, and free booze.

The RC floor is low, and the room I had as a Diamond was like on the 6th floor or so, also overlooking the park. Nice view. The room seemed larger than Robt760's pix.

The hotel was going through a remodel when I was there, so the pool area wasn't available (too bad since it was August), and they only had a very small temporary exercise facility. I understand that all the rooms have now been redone. My Diamond room had not been, but was perfectly fine, and as noted, quite large by Tokyo standards.

My recollection was that the bus to Shinjuku station was every 20 minutes (maybe just in the summer?). The walk was pleasant along a semi-underground shopping street.

Would I stay there again? Yup. Great location, and a great deal by Tokyo pricing.