Although, having an eye on Flex for some time now I had no time left to have a deeper look at the desktop stuff. It's quite interesting to find applications for AIR, even with a beta 3 release, that are fully functional, and seem to be quite stable.
Some already show, how Web 2.0 will look on the desktop, e.g. the Google Analytics Reporting Suite or the eBay Desktop. Both are pretty cool in their user experience and offer advanced functionalities in comparison to the existing service frontends.
As I'm also a hobbyist in digital studio music production, I couldn't resist to play the emulation of the legendary 909 drum computer. Pretty cool for the first implementation of an AIR application.
For me all this looks cooler than a Java Web Start based RCP implementation, whereas a Netbeans-based one was the worst in the past. Although, we have to wait for the real killer apps, like SlideRocket, to start comparing both platforms for speed, usability and design aspects.