Major features are:
Match groups using their Name, Slug, or ID
Match groups based on member response data using a flexible macro.
Add members to a specific group based on a Yes/No type of field.
Toggle automatic joining on/off without losing your settings.
A pro version is available which adds:
Force Edit Profile – members can’t navigate the site unless their profile is complete.
Group Activity Tab – an additional tab is added to the activity stream under which only activity for the matching group is displayed.
Wildcard Pattern Matching – supports using meta-characters like: *, ?, [abc]
PCRE Pattern Matching – for absolute control over the matching algorithm.
Premium Support – get professional support directly from the plugin’s author.
You can see all of Group-O-Matic’s features in action by watching the demo video at: http://vimeo.com/37754800