I highly recommend Aileen's place, the apartment is extremely spacious (I actually feel that the photos do not do it justice) and is also brand new. It has a very modern feel with a lot of room for storage and a large walk in wardrobe.
The apartment is very clean and extensively equipt with anything you would need for cooking/ cleaning, all of the amenities are very new and high quality.
The location is also great, it's on a very convenient street with lots of different shops and restaurants, including both Japanese and Western chains as well as numerous supermarkets within a 5 minute walk.
The apartment is also a five minute walk from Nakano Station, a well serviced station where Shinjuku can be accessed within four minutes.
The building is secure and safe, I have to mention that at the beginning of my stay there was some issues with the planning, but Aileen was extremely helpful and quickly reimbursed me and went out of her way to help with everything. The maintenance people where nice and trustworthy, and I wouldn't let this put you off as it is not something that would be a reoccurring problem and was overall resolved very quickly and painlessly!