How about linking IIS into Groupwise, Netware and eDirectory (along with ZEN) across multiple sites, in multiple cities, where authentication and directory services are replicated from individual trees and forests to the main tree without conflict.
Oh, and ditto for printing, browsing and helpdesk.
Yes, that's exactly what we have
As has been mentioned, IIS's 5/6's config is much better than 3/4 (what most people know) and allows for just as much control (based on what you've defined).
There is still room to grow, up IIS isn't the same beast you are obviously used to.