I looked at the AS3 version of PureMVC as an alternative to Cairngorm for building Flex Apps and found it to be very similar although a bit harder to get your app set up. The lack of data binding also seemed to be a problem since you have manually update your data to keep it in sync. I tried porting a simple Flex component I built that uses RemoteObjects and found it initially difficult but I can see how in a large app built from scratch PureMVC's light framework and modular approach in the long run will help your code be more efficient and reusable.
Thanks for your reply! In my case, what started out as a smaller project grew into a larger one.. so was looking for a solid MVC implementation, came across this one. It looked promising and had thorough documentation. The only thing was wishing it had more code examples for other languages, not only AS3.