Yuan/RMB has its weaknesses. It's a government controlled currency that's not free floating. This is good for the Chinese economy, which it could be manipulated in every way it would be beneficial. But the down side is that it damages its reputation by been not free floating.
It could be fixed by making it free floating, but then it hurts the Chinese economy since it's mostly export based as of now. Uncontrolled flotation would make it so high that majority of small Chinese manufacturing firms would bankrupt overnight.
So it's a huge dilemma. But if used properly, it could be a useful tool like the US government uses its DOLLARS.