If you plan to travel around the country, look at investing in a JR Pass. They are sold to visitors from outside of Japan, and can only be bought outside. Each country tends to have it's own dealer of such passes and being from the UK, I'm not sure where is best in Aus.
I went on my first trip back in September. I had a month's worth of things to see and my itinerary was packed. I overplanned and had no space to breathe. Especially in Kyoto where I had made it my mission to see everything. Reality was, I was all 'shrined out' by the end of day 2 (of a full week in Kyoto), so unless you have some deep deep love for all things shrines and temples, don't fill your plan up with them.
If you want to party, I fully recommend Nagoya and Osaka outside of Tokyo. Nagoya has some awesome places to chill out as well as some great places to have an action packed night. Tokyo is as expensive as they come, and Roppongi...don't even go there for the nightlife (
http://www.japanforum.com/forum/japa...ml#post798050). Hiroshima can also be terrific on a weekend, but weekdays it's pretty dead. Fukuoka...Tends to be a full on 'meat market', with it being the biggest City on Kyushu. You tend to get clubs full of US Navy from either Sasebo or Okinawa and its a pretty poor experience.
For non-partying, Hiroshima is worth a couple of days. 1 for Miyajima island, and another for Hiroshima city itself, for which it's Peace Park is just so beautiful.
Hiroshima pics from Sept 2009