We had a great stay at G-Stays Shinjuku during our first couple of nights in Tokyo. We were looking for a place that would serve as an easy home base to explore the area, and this was perfect - it was a quick walk from a huge number of restaurants and bars, including Golden Gai, and a 10-15 minute walk to the main Shinjuku station allowing us to connect with pretty much anywhere else in the city.
The room itself was nice albeit nothing too special - it was about as small as I'd expect for the middle of Shinjuku, but more than enough space for my wife and I to be staying there comfortably. David was extremely quick to respond to questions, and even upgraded our room on his own due to construction ongoing downstairs that wouldn't have bothered us at all anyway.
Overall, this was a great option for an affordable stay close to the heart of Shinjuku!