If you're sitting at a table filling a form in (and, like all "command economies," there seems to be endless form filling), the Chinese will have no compunction about standing at your shoulder as you fill the thing in (or write an e-mail or looking something up on the internet). To make matters worse, if you turn round and ask them if "they're alright there" or if you "can help them," they'll not get embarrassed about saying they're ok and continuing to what you write. I thought it was someone trying to get information from me at first, but everyone seems to do it and trust me it's irritating when they do.
The other thing I find discomforting is the fact that the Chinese teachers and kids I work with don't seem to have a feel for personal space. They're inclined to walk into our shared office without so much as a knock, and start to use the staff computers. To make matter worse, when you call them on it, it's like it's a shock to them. This despite you having a similar conversation with their best friend not 2 hours earlier (I've had more than one kid tell me that they just thought I meant their friend in particular, rather than applying it generally), and that can be irritating.
In addition, when you talk to them, people in China seem to stand 6 inches closer than they need to. If you take a step back, they'll follow you too, which can be distracting. I'm thinking about making a big thing about it the next time someone I know does it, because I find it that distracting.