Flex, CF and FDS (LCDS) work great together. For example I setup a monitoring system using Flex to build the front end graphical displays (charts, graphs, etc) then used CF Flex messaging event gateway to connect (publish/subscribe) and then used CF to push monitoring data to the Flex/Flash display screens. Its very cool!! The real magic is the push capability which means you can use server logic to control if and when data is sent -- no more polling!!