Most major restaurants and shops will accept USD dollars but the exchange rate will be lower than that given by the money changers.
Though financial transactions have become easier and closer to Western norms one may still run into some difficulties. Most changers will now take USD in a variety of conditions. However, it is still very common for bills to be rejected based on stains, folds or tears. Depending on the severity of these conditions a money changer may still refuse to change USD bills to kyat. To ensure acceptance, it is best to bring crisp, clean, fresh USD currency. A $100 USD bill will fetch a higher rate.
ATMs are available everywhere in Yangon. Please use them at your own discretion and check your card statements. The same can be said for vendors accepting credit cards. Most hotels and shops accept Visa and occasionally MasterCard. The fees for running cards may be high and there is no guarantee for the security from these vendors. It is still recommended to use cash if possible.