Last night's update brought the latest changes to the Address Book in the Basic and Professional Suite. Previously you have only been able to import clients into the Basic/Professional Suite. With the update you can now import both clients and prospective clients. You can also export your client list including clients, archived clients, and prospective clients.
If you need more advanced exporting then you should try out the StudioCloud CRM. That will allow you to filter clients according to other information such as organizations, dates, etc.... before you export them.