Well, it looks like I spoke too soon about Snow Leopard's advantages for Chinese-language users. One of the things that converted me from Firefox to Safari was the ability to use the Services menu to convert simplified Chinese to traditional Chinese and vice versa. Unfortunately, Snow Leopard broke this with its new, cleaned-up Services menu. The new menu is a very good idea--only relevant services show up now--but it doesn't seem to recognize when you've selected Chinese text, so the conversion options are not available! This is probably a Safari bug, as the options are available most of the time in TextEdit, etc.
The work-around for now is to paste Simplified Chinese text into TextEdit, convert it, and paste it back to wherever I need to use it.
If you encounter this problem, please make sure to file a bug report with Apple.