"If you want to stay near Shinagawa Station, this is the place but be forewarned, there is a LOT of construction at the station. Also, there are three towers at the Prince complex and it can get confusing getting around. This hotel is big and therefore, very busy. The lobby reminded me of Grand Central Station particularly at checkout time.
We had a room with free breakfast and the breakfast buffet (Hapuna) was a mob scene. If you have ever been to Las Vegas during a major conventions, you get what I am talking about. Long line to get in, long lines for coffee and food (though the food was excellent). We stayed in the main tower.
This hotel is a factory so you get the benefit of a large hotel in Tokyo, but it can feel impersonal and overly busy. The room was small (normal by Tokyo standards) and on a high floor we had a nice view of Tokyo Tower. It was clean (two twin beds) and the bath was modern.
It was the last stay in a three week trip to Japan and this hotel was by far the most congested place we stayed. One other thing, I booked the Prince thinking I could get a direct airport bus to Narita, but they do not stop there. You have to take a taxi to the airport center to get a bus.
The hotel shopping is good and fairly priced. There is a 7-Eleven in the hotel that is hard to find."