The WordPress Multilanguage plugin is a paid plugin that makes it really easy to translate your post into other languages.
Most theme authors don’t bother making their themes WPML compatible. Nick, founder of Elegant Themes, announced yesterday that all of the ET themes are now WPML compatible.
This is a good step for the theme community. StudioPress’ Genesis framework is already WPML compatible, along with a number of other shops including WooThemes, Themify, ThemeBlvd, and Thematic.
I personally don’t have the need for WPML, as I don’t do anything internationally in other languages, but I know there are quite a few people that do.
Have you ever needed to internationalize a blog? Which plugin did you use?