As russian user of tk toolkit, I feel much concern about i18n issues of tk. In my homepage   [http://kovalenko.webzone.ru] there's a couple of my patches, that make tk more i18n-aware (e.g. in $canvas postscript output).  I'm going to keep my page up-to-date, so any non-ascii-non-latin1 user can always find there nessesary fixes, both for cvs head and for last stable version.
----
Current i18n status/problems I know about:

* $canvas postscript is not unicode-aware. 
Patches: for 8.4 cvs head -- take patch #546910 [http://sourceforge.net/tracker/download.php?group_id=12997&atid=312997&file_id=23560&aid=546910] here.
for 8.3 stable versions, you can get it at [http://kovalenko.webzone.ru/tk-8.3.3-ps-ml.patch]

* Tk_DrawChars  on Unix is broken in 8.4 cvs head. Patch #559437 addresses this problem.