Washington Shinjuku. 10 mins walk from Shinjuku station via direct underpass.
Was in this hotel for over a week in March 2011. Didn't like it. With my wife and 2 young kids, we booked a three-bedded room but there was still so little space to move around.
Furthermore it was so warm in the room despite it being cold outside the hotel. You cannot adjust the room temperature as there was no internal thermostat. The toilet had a bathtub which was only 1 metre long max. It reminded me of the kind of toilet you see in a ship. Small and cramped.
The staff were neither very friendly nor approachable. And we could hear quite distinctly what our neighbours in the next room were saying.
What is however the worst was the fact that we could feel the room shaking during the aftermath of the great earthquake. This happened on a few nights. We were on a high floor and so the shakes were very noticeable. At one point, it got so bad that my wife told us to go in between the beds because she read somewhere that that was what you are supposed to do in such situations.
The only thing I like about the hotel is that there is a Family Mart at the foot of the hotel. Makes it convenient to buy necessities. Other than that, it was not very pleasant. The distance from the Shinjuku train station was also quite far. Not something you would like after a long day out.