You should really sit back and think hard whether you can replace Air with something like python+qt+... or perhaps java (well, the jvm+libraries, you can still write in jython or clojure or whatever's hot these days). I'm sure there must be a platform to suit your needs that isn't Air.
(1) I would imagine 64-bit Ubuntu is not rare. What are you Air app developers testing on?
There are many reasons, but the most important one is supporting Linux, since Adobe killed Air for Linux.
I have yet to see an AIR application that is truly cross-platform functional. They run, but that doesn't mean that I want to spend time in them.
I hadn't heard of hall.com before this post, but while I appreciate that (a) you've done this out of response to your users (good) and (b) you've done this because it's faster than doing something else, (c) I don't install AIR.
These days, I only want .apps that include everything I need inside of the app bundle and don't require external installations. (I say this as someone shipping a USB stick with an app that, to apply an update of the app on the stick from the Mac, you have to have a driver installed. I don't want that driver, but I have to. Can't stand it.)