I got a PowerMate for my birthday this year, and immediately tried it out with AppleScript. I wrote a small shell control script for the device that seems to work with any version of the software (I happen to be using 1.5.1, which is the out-of-the-box version). Here's the code:
To use, put the script in your $PATH, chmod it to 755, and invoke with the command line.Mac OS X Hints
http://hints.macworld.com/article.php?story=2007122622572152