I’m beginning to form some opinions of my own as I get to the point of applying it (Flash MX 2004) for real tasks. After a steady diet of books (I recommend Kerman, Moock, and Underdahl’s titles for MX and MX 2004) I have struggled to let go of a Java orientation long enough to get inside a Flash mindset and see what it feels like.
Hard to tell if the headache is from struggling too hard or succeeding.

The problem is that Flash is a mess in several respects. Flash code makes PHP look like a rigorously engineered science experiment by comparison. Code just kind of shows up in funny places, and three examples for a thing will do it three different but vaguely similar ways — I’m talking about language constructs and a lack of complexity management. The migration to the newer language features is just underway, so some of this may be transitional, but the IDE doesn’t offer so much I now take for granted in a modern coder’s tool (see http://www.intellij.com) code completion, refactoring, reformatting, syntax coloring, meaningful help, etc. The whole IDE is just nutsy, with panels that constantly get in the way and are awkward on a 1024 x 768 monitor.
I’ve started to make a few little animations for fun, and as that part sinks in I can see how it’s very powerful on the UI side in terms of what you can make, and there’s just no other way to deliver that kind of rich experience without deploying all kinds of software to the desktop. So it’s got pros and cons, and I am only scratching the surface of it after a week or so of this. But mostly I’m struck by how different a flavor it is from working in serious Java. (Surprised?)
It’s like visiting a wild country in another part of the world, where the people are colorful and like to dance and sing but the laws are a bit inscrutable and the way people drive makes you very nervous about crossing the street.
More postcards when I figure out how to make them.