Credit cards will be OK at most hotels, but not at all department stores. Call and ask the hotels first, though. Many places only take Japan-issued cards. If you book from here, though, it might be fine.
Travellers cheques are a major pain to cash... if you take them, be prepared to wait a loong time at most banks. And the rates are terrible.
Your bank card will work, but not at most banks. You'll want to find the nearest post office. Those machines work with international cards. Oh, and even if you do find a bank machine that accepts your card, be prepared for weekends and holidays and closing hours. 7-11 has 24 hour bank machines, but most close at night. Early.
Japan is still very much a cash-based country. I'd really suggest you take cash!
You can find more info at
www.gaijinpot.comOtherwise, when are you going? We'll be heading back for a trip in March or so.