We visited Tokyo in December 2012 and my wife had liaised with the staff at Citadines to book the apartment for 5 nights.
The staff were excellent, the accommodation was extremely clean and convenient (walking distance to train station) and the staff were courteous and with very good knowledge of English),
Very happy with Citadines, have already recommended it to our friends who are planning to visit Japan next year.
Will definitely go back there again

After booking many months ahead of travel (cheaper booking through the hotel website), there were a few email exchanges between the hotel and I regarding bookings for restaurants and other Japan related information and the staff always responded quickly and with very good English. The staff at the hotel are super helpful and can point you in the right direction on how to get somewhere quickest/easiest.

The rooms are well planned out and using the free wifi every day to plan activities was very good (not all hotels in Japan have readily available Wifi in rooms). We never used the kitchenette except to boil water for tea (teabags/coffee in the lobby) and the bathrooms were designed to utilise all space with a toilet and shower/bathtub which was very deep. Water heat and pressure was perfect, too. The size of the smallest room was one of the bigger ones we had while in Japan.

The location of the hotel is not the best in the heart of Shinjuku but it's convenient to getting to Ginza, Tsukiji, Akihabara, Ueno and Asakusa through the Gyoenmae station (5 min walk). It takes about 15 mins to walk to the centre of Shinjuku but it's a pleasant walk. However, if arriving in Shinjuku for the first time, one should get a taxi for about 710yen. There are lots of little restaurants and bars around the hotel and it is close to the gay district as well.

I wouldn't hesitate to stay here again in Tokyo!

Citadines is well located for local trains and shopping in Shinjuku. The staff were very helpful. Rooms are small but adequate and very clean. Do not pay for the upgraded room as they are almost identical to the standard room. Breakfast was ok but we found that the Ginko(?) restuarant located a block and a half to the left, just before the blue foot bridge was really good value and did a western style breakfast. There is revolving sign on the footpath outside it and you walk up stairs to locate it.

Everything about this hotel is great and as expected. It would probably be a 4 star in Australian standards. It has free, fast wifi & a 711 just down the road. It is safe and has an awesome restaurant district nearby. The only thing I under estimated was the distance to Shinjuku station and how far Narita airport is from the hotel. There is a subway nearby (5mins walk) but Shinjuku which is the main interconnect station from the airport line & bus drop off is a good 10-15mins walk or 900yen in a taxi. Also, Narita airport is about 1.5hrs by bus or train and the earliest they start are 5:30ish. We had a 6am flight so our only option was a 20,000yen taxi. I'd stay here again but don't under estimated travel time and distances like I did.