The main chat app of choice in China is called QQ. It is far more popular than MSN there. Only problem is that the real version puts all sorts of trash on one’s computer, and traditionally the official client only ran on Windows.
Now that there is a very basic official Mac version in beta, Tencent (the company that makes QQ) has cut off access to older protocols. This means that other apps like Adium and LumaQQ no longer can connect to the QQ service. Basically, I have lost many features I relied on, and now it really is necessary to use Windows to get the full QQ experience.
I am hopeful that things will change. There is a non functional webcam icon in the Mac beta, It would be nice to use my iSight camera to chat with QQ. I got it to work a long time ago on WindowsXP, before Microsoft broke firewire support for good.