I knew a guy in Paris who knew Esperanto. He "knew" dozens of languages, in the sense that he could read and translate the ones he couldn't speak very well. But he was the most uber language geek I ever met, and Esperanto was his friend. I've never seen it written down, before -- there's more Eastern European or something influence than I would have thought. All those "j"s. And "x"s. I would think, if you were inventing a language, you might try to go for the WYSIWYG system, rather than obscurities of pronunciation. Hmm.