I'm really not all that with it when it comes to keitais. I signed up about five years ago with J-phone and still have the same phone and same contract even though J-phone became Vodafone and now Softbank.
I've heard, like everyone else in Japan, about Softbank's new Gold Plan with free calls and email between Softbank subscribers for about 2900 yen/month. The thing I don't understand is the required "Super Bonus." What the heck is it? Do you pay for it? Is it a discount? What else should I consider as I think about a new phone plan? I'm a light user by the way.
Mobil contracts are like the Medicare plan in the states. Complicated. In the end what ever amount you end up saving doesn`t add up to a whole lot. Light user plans are good. But Docomo has the best reception nation wide. And they have world call :) Use your same phone anywhere in the world! ( Almost anywhere :)