As shown in the video, I think the best use for this new feature is in conjunction with iPhone sites. In the video, Tod shows creating an app for http://i.brightkite.com/. I've been using this to check-in on BrightKite. It's nice, unobtrusive and easy in lieu of BrightKite's own, native desktop apps.
My other favorite (pictured) is http://i.rememberthemilk.com/. Remember the Milk's iPhone app has a nice feature that the "Today" tasks list also shows overdue tasks (which I haven't figured out how to do in the standard web app).
More and more of my webapp usage is moving to fluid these days. I can't say enough good things about this app. And google gears support is coming!!