I have just checked how they do at Baidu Baike (the well kown Chinese online encyclopedia) :
http://baike.baidu.com/page/userlogin.html#reg
Their captcha is a set of 4 characters : either arabic numbers or latin capital letters. It looks easier than our current mediawiki captcha, and they have a "You can't see?" button providing another try.
2011/2/5 Liangent liangent@gmail.com:
I hate the case that I'm asked with a Chinese captcha when I'm surfing some Chinese websites without IME available.
Besides I don't prefer Chinese captchas personally because Chinese characters usually require more key hits.