We just finished a very interesting hybrid application called Ilio Fun Facts for the Army Corps of Engineers (mahalo to Native Hawaiian Veterans for pulling us in on the project.) The project provides free MacBooks to a group of public grade schools in Waianae. The MacBooks have special logins and screensavers that help educate kids about unexploded ordnance. In addition to being technically interesting it was one of those projects that makes you feel good because it helps the community.
The desktop client uses an embedded browser for the questions and the associated images. It uses native APIs for things like text-to-speech, the screen saver, and kiosk mode. The ability to update content after the app has been deployed is incredibly useful. My initial thought was to do a pure Cocoa client and simply integrate the data via webservices, but the hybrid architecture proposed by Pat (our CTO) turned out to be much better. We enjoyed faster development velocity and we can update 95% of the app functionality on the server without having to redeploy anything. This is the third hybrid client architecture we have used. The first two were for banks - one Swing / Firefox app using the excellent
component from JadeLiquid. The other was a WinForms / IE reporting app. In all three cases we were happy with the end result. Hopefully Adobe Air and standalone Silverlight will evolve to the point where we can do everything in a more integrated manner, but for now, when you need access to native code / resources
the ability to update from the server, hybrid apps are the way to go.