Personally I'd prefer an approach similar to PhoneGap -- extend javascript for the added functionality the hardware provides and base UI development on current web standards like HTML and CSS (preferably HTML 5 and CSS 3). With an approach like that the learning curve is reduced for people who don't do AIR/Flex development. I don't have the numbers, but I'd imagine the number of people who do web app development using web standards are higher. Even if it isn't the case, skills with HTML, CSS, and Javascript have a much wider application.