This has a lot of potential. Needs a lot of refinement: add groups, better/fuller control of users from the back-end (i.e.: disable, edit, add to group, etc...), and sync with WP users would be great. I also found the gratuitous, irremovable links to developer a bit annoying. If the plug-in is useful, donations will come (no problem with leaving the nag in the admin area but don't want it displayed to site visitors). Finally, I have not yet been able to send a message. Although the plug-in indicates that the messages are being sent, they are not. I have disabled this plug-in pending further development.