Flash and Cocoa
Even though I use CS4 with my clients, I still have CS3 on my own laptop because Adobe took away my favorite feature from Photoshop, and put it in Bridge, which makes my computer run very, very slow.
Yesterday, I had the most frustrating experience with Flash, and then I found this link:
In a nutshell, Eric Socolofsky summarizes what is supported and not supported (found on ITP list)
Saving images to Photo Library
Cut / Copy / Paste
Embedded HTML content (via webkit in Adobe AIR).
Dynamically loading SWFs that contain ActionScript
Video Camera Access