I have been there as well.
My experience is that Chinese ATC works fine when everything goes as planned. Any request out of the ordinary will be denied, the answer will mostly be "stand-by" in stead of "negative", they don't like saying no. They also don't take initiative.
I had to divert over China once due to WX at destination, asked several times for reroute, each time was told "stand-by" The second I called "Pan-pan" I was almost cleared direct the alternate. I am sure he was waiting for that call, so that any responsibility was taken out of his hands..