First I want to say thank you to the developers of this awesome plugin. It's certainly come in very handy.
With that said, I wonder if the user interface could be improved a bit to something more WordPress-like and user friendly for non-developer types that might be interacting with it. I'm a big believer in the KISS principle.
Here is an example of what I might suggest:
http://harvesthq.github.com/chosen/
There is even a WordPress plugin for it here you can study:
http://wordpress.org/extend/plugins/chosen/
Just an idea.
Cheers,
Brian