Development on RubyOSA has been very active recently. It's almost ready for prime time, and I will make a first public release soon.
Various improvements and fixes were introduced, such as the support for passing filenames, converting records to hashes, minimizing the send of events by implicitely resolving object specifiers only when it's necessary, plus lots of small but important fixes. The sdef parser has also been rewritten using libxml-ruby, which makes the execution speed more efficient (at a glance it's 2 times faster than REXML). There are new examples, like as a QuickTime fullscreen player and a script that fades the volume of the current iTunes song (if you did attend WWDC, it should perhaps ring a bell :-)).
I received valuable feedback from people (even patches sometimes!), this is great. Please grab the latest bits from SVN if you can.