Following in the footsteps of Mark Rees and Andy Todd, I am posting my OSDC 2005 presentation, Six Things Groovy Can Do For You (pdf). Enjoy!
I think my biggest complaint with Groovy is that people will almost always want properties instead of fields, but the @Property attribute is required for this.
This violates the idea of "make the common case fast" and will lead to extra pain that could have been avoided (or could still be if things aren't final).
Your paper is also available through the CGPublisher site now. I've not notified the paper authors yet, sorry!