this is my suggestion to compete exchange in point of view of full rich features. It is required to bring Archive Management Feature in it to bring more clients in here.
i have already suggested a feature related Group Membership removal should be easy to attract user. it is very pathetic method to disable user and find the disable users in different group by clicking and searching.
or you should introduce searching method of email clients in group to remove users easily.
kindly consider both suggestion to improve this product....

regards,
Tanveer Hussain