It has considerably improved the performance on websites I've created. I haven't witnessed problems concerning backward compatibilty either. An intense OOP application I created using flash remoting, CF processing, and mySQL still functions flawlessly. So far I love it. I've aslo played around with some of the new effect features and can say they will definitely add new creative possibilities in the future.
yes, there seems to be a reasonable speed increase on my previous work.
i too have been playing around with the new features, but i cant seem to get
the bitmap caching to work. have you?