Had a great stay here in Tokyo. We were a group of 5 friends traveling together and this couldn't have been better. This is s lot of room for Tokyo, all the rooms are in lovely condition with comfortable beds and lots of space for the city. If is great to have this amount of communal space for your group in somewhere so close to the action of Tokyo.
The immediate area around the apartment is really nice and quite but there are a couple of places in easy walking distance where you can still get a latish drink (Fungos) and really good Ramen til late if you want to.
Location is great for loads of Tokyo stuff. 10 mins walk to the subway but keep track of the fact that nearest is Nishinjunku gochome and that is not the main red line. You can get to Shinjuku station easy and from there anywhere (but you will get lost there, guaranteed). My advice if you are pretty mobile, walk or catch the bus to Shinjuku rather than go by tube. It'll take the same amount of time and you'll see more.
We had an amazing time here. It's a brilliant place to explore Tokyo from and still be able to come back to somewhere quiet, comfortable and easy. Communication from the host is near instant. Stay here, it's great.