As mentioned in this article by Thomas Enebo, Windows platform becomes the first-class platform as same as Unix, Linux and Mac OS(These are de-facto platforms in OSS-develop) since JRuby 1.7.0. Ruby-lang in the JRuby goes green almost. But some gem libraries are not yet. So this article calls for gem library developers to treat Windows platform.
Since version 1.9, CRuby deals String class with including its own encoding. And since JRuby 1.7.0, as mentioned in this article by Charles Nutter, JRuby also deals it in the same way. It's useful way if you are reading, speaking or writing in non-western language (for me, these are in Japanese). In the current release - JRuby 1.7.0 preview2 -, It's working good for ASCII and UTF-8 characters and encodings. But It has still a bit of bugs with non-western languages and its encodings.
So I hope, if you are in non-western language(Japanese, Chinese, Korean, Arabic, Hebrew and so on), I would like you to download JRuby 1.7.0 preview2, then try and test some Ruby snippets about String, IO, or its related classes, with your own language and its encoding.