So, that sounds fairly similar to "unicode in $arbitrary_language": Unicode is supported internally; there is still complexity associated in getting data decoded/encoded when bringing it in/out; new versions of the language are working to reduce the complexity but somehow not there yet; handling of unicode by libraries tends to be inconsistent and probably undocumented.

Someone should do a comparative analysis across languages. My guess is that (in-browser) javascript is probably one of the few languages to not have significant unicode problems, although there are surely some.