Pros: Located near the Shinagawa train Station which is convenient for accessing other parts of Tokyo. Take the west exit from the station and go up the street where you can see Prince Hotel buildings. Go past Outback, Singapore Seafood, TGI Fridays, etc and you'll find the hotel on the right.

Con: Located uphill from the train station. At night, lugging heavy luggage, it seemed like a long way. Should have taken a taxi. In the morning without luggage, it was a pleasant downhill walk. We didn't actually do anything in the Shinagawa area, though, other than eat and sleep so next time I might try to find a hotel in another part of Tokyo.

Pros: Convenience store located onsite
Con: Food is expensive but there are many, many options only a block or so away.

Pro: Nice size room; nice shower flow and hot water; robes & tea provided
Con: Furnishings are rather industrial and the public areas are a little tired. This is a convention type hotel.

Pro: Limousine Bus is available to the airport.

Conveniently located next to the Shinagawa Train Station and to the Takanawadai Subway Station, you can reach a lot of places from here.
The rooms are big and clean. There's a small balcony available as well, and the bathroom has a big space.
The internet is fast, and as common with Japanese, the personnel are very welcoming and sympathetic.
Do be aware of breakfast, though. It is not included, and there's a restaurant on a lower floor from the lobby that serves it. You end up paying 27€ for a breakfast that is only “normal”, and that it certainly doesn’t live to the standards of such requested price. You better just buy stuff from the convenience stores located on Shinagawa Train Station. There's an Outback Restaurant just across the street in case you're in for something more western.
I'd definitely stay here again.

Stayed here during my trip in November for 4 nights and booked the superior twin room with 10% discount of the normal rate. Counter staffs were very polite and efficient, they will always greet you whenever they saw you. But command of English still need slight improvement. Room was in a great and clean condition when I checked in. Surprised at how spacious and clean the room was and there is even a balcony. The view from the balcony was great and the leaves on the tree was starting to turn red. The facilities in the room: mini bar fridge, safe, hotflask, 32" LCD TV, a big n clean bathtub, closet for clothings, a desk for writing, a single seater sofa, a coffee table and 2 super spacious bed etc.

Location wise is not bad, but if you are with a heavy suitcase, then the gentle slope to the hotel from Shinagawa JR station might prove tiring and abit challenging. Getting to the hotel from Shinagawa JR station is around less than 10min and to Takanawadai subway station is nearer. The vicinity of the hotel is full of restaurants and cafes but nothing much for you if you want to shop. There is a 7-11 convenience store in the hotel which opens till 2am so no worries if you are hungry at night. Sadly, there is no free wi-fi. You can bring a laptop and connect using your own ethernet cable. If you do not have a laptop, you can use the desktop PC at the business lounge (100yen for 10min).

You can also book the airport limousine bus ticket from the hotel as it is one of the boarding point to Narita or Haneda airport.

Overall, this is a great hotel with good service and nice rooms but location wise is ok if you do not mind daily traveling to Shibuya, Shinjuku, Harajuku etc. It will be great if wi-fi is provided free.

We recently decided to spend a week in Tokyo on our way back from a trip to Canada, we asked our travel agent to book as 3-4 star hotel close to transport and she recomended the Grand Prince New Takanawa.

We found the hotel to be very pleasant, and definately handy for Shinagawa Station, only about a 3-4 minute walk away.

The guest relations manager Nami Kawano was a gem. She was extremely patient with my constant hassling for information, gave us maps for everywhere we wanted to go, wrote notes in Japanese for us to give to taxi drivers, etc, and recomended some awesome places for us to visit.

Food at the hotel was excellent, breakfasts at Marmolada was excellent quality and great value for money.

Our room was always spotless and we had a (little) balcony to take in the morning air and got some great sunrise / sunset views.

The gardens between the Grand Prince & Grand Prince new were out of this world, we actually walked the long way to the station just for the pleasure of walking through the gardens!

all in all great value!