Alex, I suggest you consider adding a sortable/groupable grid control to compliment the ThumbnailViewer/AnnotationViewer. The grid should show (in real time) additions/changes to the annotations and can be exported to xml/csv/excel. In my view anyone who wants a line of controls that can scan/show and annotate images must have some uses for the annotations. Such a control will will make your line of products complete, and be able to compete with any other similiar products in the market.
Re: New features request for version 2.0 of VintaSoftAnnotation
The AnnotationCollection class have two events: CollectionChanged and CollectionChanging. You can subscribe to these events and receive notification when new annotation will be added to the collection or an existing annotation will be removed from the collection.