China is not the only country with metric units. The whole former USSR does it. Most of former Eastern World did it.
We flew only to Southern China. There you don't have kilometres. Possible that only our charts where recalculated, but they where in NM.
ATC around Southern China (Guanzhou - Hainan - Hongkong - Xiamen) is quite good. Very professional staff, of course not the same as here but not too bad compared to some other Asian countries.
Dani