smart+question
The current "Edit Groups" dialog can be made better. It now has single list of 'Groups', with a checkbox for each. To add a group to the contact, the user needs to 'check' the checkbox corresponding to the Group.
I propose a different UI as follows
Lets us have two lists. One is "Available groups" and other is "Groups which the contact is part of". Let us have two buttons (array in both directions) in between them. This way the user could easily add Groups for the particular contact.
One advantage of this: Suppose if there are a large number groups, the user could coherently see the groups that the contact is assigned without scrolling the entire list.
One a complete unrelated sidenote, we can have something like this for 'message-to-many' dialog too.