The new Snow Leopard has a nice new input system for inputting Chinese: You can write characters directly onto the track pad with your finger. To toggle to handwriting input, press Control-Shift-Space... apparently. Unfortunately, I missed the part where Apple told us this would only work on multi-touch track pads--ie., those on newer MacBook Pros, MacBook Airs, etc. My old first-generation MacBook doesn't support Chinese handwriting input.
The good news is, though, that the Pinyin input system seems to have been updated. I haven't messed around with it extensively yet, but it seems to be better at predicting which characters you want, and, when inputting Traditional Chinese, you no longer have to put in numbers for tones. (I think this is how it always worked for Simplified Chinese.) Just type in "nihao," press Space, and it knows you want 你好. I actually prefer to type tone numbers so as to limit the number of candidates that come up, but I could see how in some situations this could save you some time.