I think I stopped developing Flash at around version 7 or 8, right around OOP programming languages like Java and .NET became mainstream. I saw Flash as a difficult to maintain application, great for small controls that needed a cool way to present "stuff". I would never build a complete application on it because ActionScript and working with the timeline control was just a pain. Instead I would always look for alternative ways to keep the web application dynamic through the use AJAX or even applets if needed.
I was lately re-introduced to Adobe Flash once again, this time with the new Flex framework. I was astonished to see how closely it resembled to ASP.NET and C#/Java syntax. It's fully object oriented, coupled with a great IDE like Eclipse, you can now drag-and-drop controls to build the perfect client-side application that is dynamic, interactive and functional fast and easy. The source behind the GUI is XML based so it resembles a lot like ASP.NET. Controls have pre-defined events that know to react on user actions and page loads. It's very intuitive and for a season Java or ASP.NET developer, the learning curve should be a breeze.
This comes at the right moment as I was looking for a cool way to create my next financial application with graphics and charts. I'll take a stab at Flex and see if it is truly as easy as the Adobe videos demonstrated.
To find out more about Flex, check out http://www.adobe.com/products/flex/ and http://www.flex.org. Flash is an open source format so it's no surprise to find some free IDEs or you can buy the Adobe tool for $499 about the same price of a Visual Studio.NET.