Mac OS X is finally up to speed with Traditional Chinese input. You can now input with the “Hanyin” input method. The Hanyin input method existed in Mac OS 9, but hadn’t been implemented in Mac OS X until now.
What does the Hanyin input method let you do? It lets you type in Hanyu Pinyin with tones (i.e. “wo3”). Learning mode can be turned on where it guesses what you are trying to type from multiple dictionaries (i.e. general dictionary, Chinese medicine dictionary, military dictionary, Western medical dictionary, Buddhist dictionary, information technology dictionary, industrial technology dictionary, horticulture dictionary, etc.), thus helping those out who have limited character recognition. It also learns from the characters you most often input and presents them as first choices before you have to hit the space bar and input the right character from a list of other options with the same pronunciation and tone.
There are also a host of other tools implemented for developers that need to have an overview of properties, incorporating fonts, input sequences, Unicode, etc.
On a related note, system wide checking of spelling as you type has been implemented. For example, you can have your spelling checked in your Web browser as you type, just as you would in MS Word. Just do a CTRL click to bring up the properties menu. Or, just right mouse-click.