I just found an important difference, (to me anyways), between the old and new clients. We use an address book with a number of sub groups contained therein. In the old client there was a " " sign beside a top level address book, and I could expand that address book to display the groups with in it. This allowed me see click on the "GroupWise Address Book" to see all of our clients in the right pane, while in the left pane I could see the sub groups under our top level address book at the same time. I could then easily drag and drop new users into their appropriate groups. The new address book doesn't allow you to expand a top level group.
If someone could give me the right to post an attachment, I could illustrate this a bit easier.