I blog in two languages (English and Bulgarian), and I use two blog installs for being able to do so. I was in research for a good stable plugin a year or so ago (found ‘Gengo’, btw, but its development lags very much behind latest WP releases), but didn’t find anything which would have given me complete control, stability and ease of use.
So I just installed two blogs, and cross-linked them. I write in one of them, when I want post in English, and in the other, when I want to post in Bulgarian…
So, sorry to disappoint you… I think WP has still a long way to go, before starting to support multilingual features out of the box…
Still, there are a lot of good dev solutions on how to install multiple WordPress’es with just one copy of WP, so this might work for a multi-lingual blogging, as well… Just go through the various solutions carefully:)