I had avoided upgrading the Flash CS5.5 for a few months because the job I had didn't really need it and I had been exploring Corona and Cocos-2d for iOS development. Then, just last week, I was asked what it would take to translate a client's existing kids web site (Flash animation, games, etc) to the iPhone. Having done this quite a few times to create HTML5 versions of Flash sites I knew that the process was tedious at best no matter what target development platform was from Flash. There just are not any really refined, robust tools to get a detailed swf animation or set of designed interference widgets from CS5 to HTML5, Corona, or any of the other other iOs (or Android) targeted systems. Even when the assets are exported easily, coding them to work the same as ion Flash in a monster job.
The process usually includes taking timeline assets and exporting them as a series pngs, and then using what ever language constructs exist in the chosen dev platform to re-assemble everything into a workable solution.
I had heard that the CS5.5 and Flash Builder 4.5 Air to iOS package was getting some good results, but I was skeptical because the tests we did with Flash CS5 were terrible. The same basic code and assets that would run in Lua in Corona at 30 FPS and 15 FPS in HTML5 would run at 5-10 FPS in the CS5 export ipa file when tested on a device.
The new CS5.5 Air exporter (works only with iPhone 3+ and iPad Devices though) is now giving me pretty much full frame rate results on the same games, app and animations that once ran at less than 10 FPS.
This is very encouraging and we are continue testing to see if we can get enough special fx, animations, and game-play elements into an Flash CS5.5 to iPad device to convince the client that this is a viable solution.
One last thing...it does NOT support AS2. If you do decide to take all of your old games and flood them to the iOS market, you will need to upgrade them to AS3.