Way back in the days of Macromedia Central some of the Flash community were requesting some things that at the time we thought were huge..
- the ability to have the apps show up in the Start menu, shortcuts on the desktop, etc like a real app
- the ability to totally skin the app window (remove the Central chrome)
- a lightweight, built in database for handling large amounts of data, extra bonus if it handled SQL
- a way to securely store data on the system on a per user basis
- better performance both in video and in ActionScript
- free (as in beer) like the Flash Player instead of buying licenses for Central

and others.. I can think of these easily though because these are some of the requests that the folks at Macromedia sat down with us and listened to. The result is AIR, and most of those features I listed above are pretty well known features of AIR already. Here Christian Cantrell gives some info on the "how to securely store data" part in AIR. It might seem like a small feature, but it's a big win for some folks. It's certainly possible to roll your own solution, but it's nice to have a standard, built in method.