I've just returned from a weeks stay at the Sunroute Plaza Shinjuku and I couldn't fault it. As the other reviews have stated, yes the rooms are small but you have to put it into perspective. Most rooms in Tokyo (unless you want to pay mega dollars at the Park Hyatt) are not much more than shoeboxes! The Sunroute is centrally located, is within 5 minutes walk of Shinjuku station and has a good selection of Western and Japanese food options in the area.
If you're after all the bells n' whistles...a huge room service menu, day spa, multiple channel TV, gym, concierge...then this isn't for you. On the other hand if you're after a clean, contemporary and well priced hotel with friendly English speaking staff then this is the go. Make sure you check out the guest lounge area on the second floor. A great free coffee/tea machine and internet access along with comfortable lounges. The bar on the second floor is also cool.
The other advantage of the Sunroute Plaza (and this may also apply to other hotels) is that the Limousine Bus to Narita Aiport stops right out the front. It costs about Y3000 and was for me, the easiest way out to the airport.
A two minute walk across the road (behind the Hotel Century) there are new Starbucks and Krispy Kreme. Personally I'm not a fan but others reading this may want to know. There's also a McDonalds on the way to Shinjuku station. My advice is to avoid these and try some of the street fare nearby...the noodles and the yakitori are excellent. Or you could grab some Japanese rice crackers and some cold Asahi from the AM/PM across the road and watch hilarious Japanese game show TV.
I had a great experience at this hotel and will stay here again next time I'm in Tokyo. Have a great time.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.