I'm still looking for Windows testers (reported as working on Mac OSX, and I know it works on linux). I have created an alternative vendors Rakefile for windows users here just in case that is holding you back.
NB: Currently this is the only way of getting processing-2.0 version of ruby-processing (and this may not change for some time as the creator of ruby-processing Jeremy Ashkenas is on the road for 2013 last reported in New Zealand, and he's also got Coffee-Script to look after).

... and he's also got Coffee-Script to look after.

I've taken a look at Coffe-Script some monts ago. It's so much cleaner than JS!  
Still, gotta take a look at Dark as well some other time!  

For Mac Windows users/testers I have also bumped up to the recently released processing-2.0b9, however I'm experiencing  issues with processing-2.0b9 on linux so I have provided an alternative Rakefile (to retain processing-2.0b8).