Stayed there for 2 nights for business travel. Located in Roppongi it is great if you have time to enjoy the night life (unfortunately it was raining non-stop when i was there, so did not really feel like it). Overall design is very modern, rooms are modern with open bath room - to be closed by sliding door. Sleep comfort just average.
One tip: if you want to watch English speaking channels on your TV, you need to press "Hotel channels" on your remote as otherwise your are stuck with japanese only.

The location of the hotel is great if you don't speak Japanese as this area is better situated to accommodate non-Japanese speakers. Plenty of shopping, restaurants, and night life nearby.

The rooms were clean and wifi worked fine. Concierge and staff were friendly and knowledgeable when we needed information on restaurants and directions.

The main asset of this hotel is its location in the heart of Roppongi Hill.

The hotel is Japanese efficient, stylish, yet the rooms are small with surprisingly a lot of wasted space. There is a very wide and long hallway leading into the room that other than using when you enter and exit the room, for the rest it’s dead space.

The Club Rooms are located on the 10th floor, which has a wonderful lounge area, yet I do not understand why the club rooms are so low down, where you hardly have a view. To me it would make more sense to have them on the top floor, like in many other hotels, where you could at least see the entire Tokyo Tower and not just the top-third as was the view from our room. Can’t help it, I’m a sucker for views!

If you have no time for sightseeing, take at least an hour and go to the adjacent Mori Tower. The Sky Gallery and Sky Deck on the 54th floor have the highest open-air observation deck in Japan. From there you can see the full 333m Tokyo Tower in front of you and in the distance the soon to be opened (May 2012) Skytree Tower, which at 634 m high is currently the second largest man-built structure in the world.

Now why didn't I have this view from my room?!