We found that US dollars were the preferred currency.  Be sure to bring only clean and crisp new bills.  Bills with the slightest wrinkle, stain, or sign of wear will not be accepted.  Do not even fold or roll the new bills you get from your bank.  Also, Doug, if you will be traveling with a female, suggest that she bring along all of her old lipsticks.  Almost everywhere in Myanmar, young Burmese girls will approach foreign women and very gently, shyly, and politely ask for lipsticks.  A lipstick or two can also provide great barter opportunities.