I have a plugin that does a little work after a user has been saved in the CP based on the user groups they are in.
The $event->params['user'] object seems to be partially up to date when the event is handled. The username and general info is the recently entered values, however the groups is not current, it is always what is was before
$_POST['groups']value, and the order in which it's processed. This answer from another question addresses a slightly different situation, but may help you solve your problem. – Lindsey D Aug 26 '14 at 23:12$groups = craft()->request->getPost('groups');– Derrick Grigg Sep 05 '14 at 13:51