The place is worth it!
The location is the best. Really close to the JR Shinjuku station and to the Shinjuku sachome metro stop. Les than 5 minutes away from both, a Family Mart just downstairs, 2 minutes away from the Shinjuku information office (where you can get the metro card, maps, help to call places where they just speak Japanese...).
The stay is quite big for Tokyo, with enough space to leave the stuff and a huge confy bed (1,80x2,15m). It also has the typical Japanese toilet with heated seat and all the mod cons.
The host is really helpful, he gives all kind of information in advance and during the stay (including videos explaining how to get to the apartment) and answers all the questions really quick.
One of our best choices in our trip to Japan. We'd definitely choose it again.