Some additional information/documentation is at http://translatewiki.net/wiki/Page_translation . An overview of translatewiki's translatable pages is at http://translatewiki.net/wiki/Special:PageTranslation
The translatable pages can also be exported as gettext file for offline translation, and the translated gettext files can be uploaded again through http://translatewiki.net/wiki/Special:ImportTranslations ('translate-import' access right needed).
Like annew says, there probably are quirks, because the feature hasn't been used on a large scale; mainly because no production wikis that have a significant volume of translatable pages are using it yet. Help on further development is appreciated. Translatewiki.net's purpose is getting user interfaces translated, so we only use it for our most basic documentation for translators; we'd rather have them translate UIs than documentation of the wiki itself.
Siebrand