We used AIR for making graphical user interfaces on embedded devices. From a technical point of view I can only recommend it: AS3 is a good language, Flex and MXML are easy and straightforward to work with and there is good tooling included.
However the downside of AIR is really future-proofness: Thanks to bad publicity and the assumptions that all flash can be easily replaced by HTML5 the development of AIR is continuosly phased out. E.g. AIR for Linux (not Android) is already no longer supported. I don't know how active the development now is under the Apache umbrella.
Alternatives would be:
- Xamarin (.NET)
- QT (i enjoyed it less then AIR because you have to switch between C++ and Javascript whereas in AIR you can implement your whole app in a single language)
- use one of the HTML5 frameworks in combination with typescript (you will need quite a lot of JS libs to get what AIR brings you straight out of the box - but on the other hand you are more flexible to choose what suits your needs)