I don't really understand AIR. Isn't it just an animation engine that's had a programming language bootstrapped to it, and then flung onto the desktop? Seems a little too hacked together for me.
If you are a web developer and want to leverage on your existing knowledge to target desktop market, AIR is the way to go.
You dont need Flash/Flex to build AIR apps. The Air SDK is available cost free at adobe.com/products/air/tools/sdk/ Or you can use aptana.com/air
A comparable open source tool: titaniumapp.com
BTW, for anyone hacking AIR on the HTML side, check out ExtJS. Best JS framework I've seen for developing apps that look "app-like".
AIR is another attempt at the age-old "write once, run anywhere" concept. One reason I left HTML/Javascript web design and got into Flash was that I wanted the incredible luxury of writing for a single platform with a single set of implementation quirks; AIR is an attempt to extend that luxury to the desktop.
It's got quite a few steps left to take; the runtime install is seamless and only happens once, but the app install screens are needlessly scary, as we've discussed before. Still, for many situations AIR is not an unreasonable choice.