I guess I'm the voice of dissent again.

Use your credit card for large purchases, like hotels and such, even though you will get raped by the international transaction charges. But get and use cash for day-today expenses. You just don't want to whip out your handy-dandy, uber-platinum credit card to buy a bowl of ramen at the little place in the alley or to pay the 500 yen entrance fee at the tourist site of your choice, or to pay for that 1000 yen taxi ride. Get cash, use cash.

As for travelers checks, they are still one of the cheapest options for exchanging cash at the airport. If you can get no-fee t/cs, you will actually get a pretty good exchange rate from the airport bank outlets (not the FOREX booth.) Just don't fool around with trying to use t/cs during your travels around. Exchange them for yen at the airport and be done with it.