I have been using Flex / Flash Builder for a number of years. The latest release of Flash Builder (4.7) seems to come with quite a few problems, the biggest of those being:
I actually have become quite fond of using RobotLegs.
In my MXML views I try to keep all logic outside of the MXML and simply dispatch events out to the mediator. From there I can put code in the mediator to the heavier AS needed.