Check out the video on the Zillow iPad App.
And read the CEO Rich Bartons blog post about it.
I believe the iPad could be used extensively to display real estate listings (i.e. photos and maps) for clients. For example, in app like Zillows.
Furthermore, a great way to use it would be at conventions, seminars and so on to walk around among the attendees and show something online or just slide through a presentation.