My multigaming clan has been using different VOIP softwares over the years now and Mumble is definitely our favorite. Though we do really wish it had a User groups feature. I mean, you can already have groups but it would be lovely if you could assign different images/icons to those groups and they would show up in the users who belonged to those groups. If you mouse over the icon and hold there for a second you should also be able to see the group's name.
The screenshot shows an example of what I would love to see.