While Alt-tab is useful, a visual tab interface created by dragging a Prism window over another to 'unify' them into a single tabbed-window would be nice (see panel interface in Dreamweaver).
Also - you still need a 'web desktop' place where you can login and your desktop of Prism windows automatically popup if Prism is installed on a system. That would be a nice unifying interface for mobilites like me.