Just an update on where the Mavericks update for GrowlMail is.
Code on GrowlMail is complete at this point, working on two issues with the Growl framework itself.
the first issue is that it spews on launch about trying to register with growl while an attempt is already in progress
the second issue is a crash after a few growl notifications are sent
I believe i have both of these issues resolved, but I'm going to take another day to verify that they are indeed fixed before I post 1.4.
the upside is that in moving to the newer framework, notifications coming out of GrowlMail will be able to reveal the message in Mail via clicking on the notification again.