Its a good place to stay. Detailed review bellow:
The home is very close (2-5min) to the station, easy to find, very convenient location. There are many konbinis and restaurants in that area. Please note that the station is not Shinjuku but Shinjuku-gyoemmae, its 2 stations from the main Shinjuku area.
The home is on 4th floor, there is no elevator so it may be a serious issue if you have lots of luggage. The staircase and corridor are a bit old and unpleasant, not dirty just not very welcoming.
The room itself on the other hand is really clean, cozy and feels much bigger than on pictures. Its equipped with everything you need. Well.. its still a tiny studio but you can feel a separation of kitchen, living room and bedroom zones. Bed is a double bed, very comfy, clean, fresh, quiet (other comments mention noisy bed - but i guess it was replaced because current one is really comfy). There is a big window on a street - its a well-urbanise area so the view is basically a buildings on the other side of the street, but its not like window-to-window so doesn't feel claustrophobic. Floor is clean, nice to walk bare foot, homey feeling.
There is a washing machine IN the room but it was very quiet. No drying option. Bathroom is very tiny, relatively typical Tokyo style bathroom so do a research because some comments mentioned its unusably tiny but its really just a normal small Tokyo bathroom.
Pocket wifi is a nice plus.
Checkin process went very smooth, good communication, quick responses though it was very strict and robotic. I guess they had bad experiences in the past thats why they are very strict and defensive. Automated, using some external managing company, definitely not a home stay feeling, just the business.
Many comments mentioned strange odor, thats unfortunately still an issue. Not sure if its bathroom or kitchen, but from time to time its really strong and unpleasant especially compared to overall cleanness and coziness of that place. I stayed just a few days so didnt care that much but for longer stays it could be a big issue.