Stayed in a standard twin room during January 2012 for a week. Rate was half the price on their website, through one of the bigger booking sites. For what we payed, it was totally worth it. Room was spacious for Tokyo standards and had all the amenities you would expect from a Japanese hotel, like free toothbrushes, toothpaste, washlet, hairdryer, electric pot to boil water, thee bags etc.
The fridge was big enough to store a few lunchboxes and drinks, which was all we needed.
The location is extremely good, it's practically connected to Shinjuku station, which is one of the biggest shopping, dining, transportation, entertainment and business hubs. You can get to most locations on Tokyo without transfer or only one transfer of trains/subway.
For breakfast we went to the the 24hr Denny's behind the hospital at the back a few times, where you can get Japanese or Western breakfast for around 500yen or less. We didn't try the hotel breakfast, which is around 2000yen.
The hotel's address is in Shibuya ward, which neighbours Shinjuku, that is why it is sometimes listed as Shibuya although it is right near Shinjuku station.

The high reviews from Trip Advisor are spot on. Hotel Century Southern Tower was by far our favorite hotel during our 2 week trip to Japan (disclaimer: this excludes our one fabulous night in the Ryokan Tanabe in Takayama, and applies only to standard hotels, not ryokans). When we arrived off our 14+ hour flight, it was so nice to find the hotel so easily, and just steps from the Shinjuku station. We took the elevator up to 20th floor, and really felt like we were in modern skyscraper Tokyo. We checked in a little early, and were able to go right to our room to take a nap. The lobby and hotel bar were both very sophisticated. Our room was on an even higher floor, and had a great view of the city. It was large, and had a nice table and chairs, and great bathroom. Everything was immaculate (well yeah yeah this is Japan). The bed was very comfy, we slept great, and therefore adjusted to the 13 hour time change rather easily. The receptionist even helped us order a pizza from Pizza-La one night. We got a reduced rate from hotels.com. Fantastic hotel.

Good location, easy access, big room compared with others hotel in Japan!
but the service of the staff just so so.

Had a stop over in Tokyo after a skiing holiday on weekend of 21/22 Jan 2012. This hotel is in a great location, easy access to the JR, Metro and Narita Express and directly opposite lots of shopping if thats your thing... This is a slick new modern hotel.
Rooms were fantastic for a Tokyo city hotel, very spacious, well equipped and super clean and tidy. Rooms start on the 20th floor and although the weather when we were there was overcast with low cloud, we had great views of the Tokyo skyline (bonus). Beds are super comfy and these rooms have to be some of the quietest hotel rooms I have ever stayed in ... anywhere. Plenty of amenties on site. Staff were great and we would definitely stay there again... Highly recommended.