Started my first serious app with Flex 4 and i can`t tell how much I enjoy it.
Have not heard so many AHHHS, WOW, F$%CK Yipiiiiiiiee from myself while developing for quite some time.
Don`t really want to add to the fake HTML 5/Flash is dead discussion (have not yet seen a year without this talk :-))
Only thing I can say is that great tooling and proved frameworks really matters to me…

Flex 4 – I love you!