I personally think that if anyone is thinking of developing any application in Flex 2.0 then they should consider looking at Cairngorm micro architecture.
I heard about Cairngorm for the first time in Flex 2 training session and had few doubts about its need and usability but after implementing a small Flex application with Cairngorm I’m a fan of it now 
Though it (Cairngorm) requires a little effort to learn its patterns. As other Cairngorm developers suggest, its not required to learn while one is learning Flex but once you are comfortable with basic Flex development, its worth looking.
I struggled a little in finding good tutorials and example code for Cairngorm but fortunately we have CairngormDocs.org now… The diagram explorer is the one that you should be looking forward there
