Lessons learned: keep it simple, don’t use technology for technology, don’t find a problem to your solution. Well, I got to enthusiastic about trying out new stuff, but now we are back on track.
So, 10 days for Flex, 12 hours for Rails+Spry, and 8 hours for plain Rails. Now this comparison is not fair as we spent quite some time on integrating Flex and Rails. But definitively when a Flex application becomes quite large, the compile time causes a drag to the development time. This is compared to plain Rails where you can just keep doing changes at which ever level you want (model, controller, view) and instantly see the change, resulting in a way faster development cycle. Don’t take me wrong I love Flex, but for this project Rails is a better fit.