It’s been a long time coming, but looks worth the wait. Lots of improvements and a fundamental change (enhancement) to the skinning components in the form of Spark. Although Flash Catalyst isn’t released yet, there’s still scope to get to grips with the developer side of the Spark skinning architecture in the meantime.
Although the charting components have now been open-sourced, i.e. you don’t need the professional licence to access them, significant differences make the premium version vital for heavy development e.g. Performance profiler, Memory profiler and network monitor. For more detail check the Flex version comparison chart.