Good question.
Personally, I used to love flash, but they kept adding crap to it and the IDE environment kept getting crappier and crappier (in my experience), that it became more of a PITA than a benefit, and that was even before iOS.
For sure, in the right hands, and for the right things, it's a powerful multimedia tool, especially for desktop interactive presentations. I've built many such things in Flash (and Director!) myself.
Some advice: Go ahead and use Flash, but treat it like the component it is. Don't do your entire UI in Flash, just use it for media playback, and even then as a fallback for when HTML5 standards don't work on a given user's platform of choice. That way when things really get going, you don't have an entire application to re-write. For sure the main platform that will still be around in 10 years will be the web.
JavaScript isn't that much different from ActionScript, DOM elements aren't that much different from MovieClips.
I expect we are about to see really good interactive multimedia in the browser. As a fellow tool-builder, I've got something cooking myself. Curious about your project, any details you can share about why you feel Flash is essential?
