My company, SapphireSteel Software, has just released a preview (beta ’edge’) edition of Amethyst - our Flash Platform IDE for Visual Studio - which includes new tools to let you share Flash IDE (CS4 or CS3) applications with Amethyst.
That means you can continue designing and animating using the Flash IDE and do the programming (editing, debugging, refactoring, IntelliSense) in Visual Studio. More info here:
http://www.sapphiresteel.com/Flash-In-Visual-Studio-Amethyst.
Merry Christmas one and all!