Nobody uses AIR because it delivers better-quality desktop apps. Companies build AIR apps because they're short on time and cash and wary of investing in development and maintenance that's outside their area of expertise. This is understandable, but shortsighted, and a lot of companies are about to make the same mistake in the mobile arena.
"We don't have time" is the common excuse for delivering an AIR app instead of a good native app. Money, though, can buy someone else's time. For a price, you can find a great contractor to build a native app for any platform under the sun. Yes, you have to spend some time managing the relationship with that contractor. It's an investment. Eventually, unless you've misjudged your market, the investment should pay off.
Good points all around. An AIR app is, really, the desktop app equivalent of a half assed product. Better to build on a single platform, but to build a convincing offering.