There are also cheaper serviced apartments, including one that I recall that across from the Grand Hyatt and within hollering distance of the Mori units. These also come with a kitchen -- although you will be amazed at how they squeeze everything in (sinks overlapping bathtubs, stuff like that). However, like most accomodation in Japan, they will still be squeaky clean when you check in.

I have to admit that I like the location of the Azabu Juban Oakwood units best of the ones I have seen even though there may be more luxurious apartments elsewhere. Note that this location is very popular and is often booked months in advance.