First of all, I want to thank you for creating Craft. It's really one of the best content management systems I have ever worked with.
I encountered an issue while working on a multilingual site: German Umlauts are not automatically transliterated (Ä -> Ae) for slugs. In other parts of Craft (e.g. field handles) Umlauts are transliterated automatically.
Personally, I would prefer if this behavior could be controlled by a config variable (e.g.