I think it's a good value for money in Tokyo. The location is great, you can easily get around from Shinjuku and there are a lot of things to do nearby. The underground station is very close! Shinjuku station is around 10-15min away by foot.
Even though the area is lively, it was quiet in the apartment.
The flat is rather small, but it's to be expected in Tokyo. It is modern inside and the bed is comfortable.
The conbini is literally just outside the building, but a proper supermarket would be further away and it's not open till late. Plan ahead if you need to buy something more substantial.
The only constructive feedback I would have is that the towels are old and thin.
Keep in mind that there is no reception, so there is no option to keep your bags. I had a bit of trouble with that, because I didn't plan this in advance and the coin lockers around wouldn't fit by suitcase. So I had to sit with my suitcases and wait for the 4 p.m. check-in in a nearby cafe.