Main changes:
1. All characters have been automatically checked whether they require AMS or not, so dynamic loading of AMS should be more robust.
2. It is possible to use UTF-8 inside \mbox{}, not only ASCII. I managed to render Polish characters, but it seems that more work is needed to make latex work with CJK.
Unicode packages are not available in default TeTeX installation, and have to be downloaded separately from http://www.unruh.de/DniQ/latex/unicode/
Unicode packages (ucs and inputenc:utf8) are loaded only if there is \mbox containing non-ASCII characters.
I'm not really happy about this solution, but it should at least work for English, Polish and Esperanto, and \mbox is not the most important feature.
Btw. which Wikipedias on new software haven't moved to UTF-8 ? It would be so much easier if everyone used the same encoding.