Yuan is pegged to US$. And we buy most everything from China. And the further we devalue the US$, the less the dollars in Chinese hands are worth. Forcing them not to hoard the dollar and invest in the US. In the end, we win buying things cheaper, making chinese poorer, and having great american infrastructures funded by the Chinese.
I guess if you are the consumer that buys most of the junk they sell at Walmart , you are in shoppers heaven. As long as you can afford food and gas for your car( thats what visa card is for).