I didn't like that I had to download Adobe AIR for downloading and installing your app. What speaks against making a .dmg file and allowing the user to copy your app wherever she/he likes?
2. Assuming that were possible, how is this to be packaged for Linux and Win32 such that it Just Works?
First time I looked at an AIR app I was also annoyed about having to install yet another VM thing. But, a few actually useful AIR apps later, I didn't care. So long as there isn't some creepy eternal background process running (cough Google updater cough Apple's itunes spy cough ) as residue, it's not an issue.