Be warned that the ground level of the building is populated with bars. This translated to quite a lot of noise at night (even on weekdays) until the early mornings due to drunk patrons yelling and causing a general disturbance in the neighborhood. Although this place is on the 4th floor, the noise permeates and feels like it's right next to the window. Was not a problem for me, but if you're a light sleeper be sure to bring earplugs!
No elevators and a narrow staircase. This would not be an issue for most people, but if you have mobility issues or a really large/heavy suitcase it may be a struggle.
For positives, the Host is communicative and provides easy-to-follow detailed instructions. The site is conveniently located near the Shinjuku-Sanchome station. You can transfer to the JR lines after one stop at Shinjuku station for the Yamanote line and get to many popular tourist areas. The bedding is also quite comfortable. Overall decent stay.