it would be great to have an option to mass-add users all at once. The way it would work is that you would be shown a table of all the phone devices that have not yet been mapped to users and then form fields to fill in the information for each device. You'd be able to skip any phone devices that you didn't want to input info for, of course.
There are lots of possible improvements to this system later, of course. 'Things like a user picker, maybe user account suggestions based on caller ID name (if it exists?), guess at extension?