The apartment is about what you would expect for the price of a place close to Shinjuku. I'd likely re-book here if I visit Shinjuku again.
It was pretty spacious for a one room place, definitely above average for Tokyo. The location is great - just a short 10 minute walk to the most popular areas of Shinjuku. It is also literally right around the corner from the subway station, making it extremely easy to get there with luggage.