I read online (e.g. http://www.pinyinjoe.com/linux/ubuntu-910-openoffice-chinese-setup.htm) that ibus-chewing supports phonetic input of traditional characters using the pinyin system but I cannot get it to work under Ubuntu Oneiric. The problem boils down to being able to change the keyboard type which I cannot do using the interface provided. Any ideas?
I just managed to find a solution to my own question. I still haven't been able to get chewing to work the way I want, but here is a fix using the pinyin input method.
First of all, set "Show language panel" to always in the ibus preferences. At the moment, I cannot get the panel to integrate well with unity, so it does not seem to show unless forced to. Next, one of the buttons reads "traditional" and it toggles between simplified and traditional input. Voila!
One suggestion -- since the traditional characters tend to have more strokes, they can be tricky to read to an untrained eye (such as mine). For these purposes, increase the font size in the ibus preferences dialog (14+ looks best to me).
Mine was a little different. I'm using Ubuntu 12.04.
I had to go "Keyboard Input Methods" and set "Show Language Panel" to "Always". After that, I went to any text box, pressed the Ctrl+Space trigger, then switched between Simplified and Traditional by pressing the "简" icon (changes to "繁").