AS3 was up to 10 times faster than its predecessor.
Flash Player 9 could run older AS1/AS2 content (via AVM1) alongside AS3 content (via AVM2) in the same SWF. flash version 9 0
It paved the way for more sophisticated H.264 video support in later sub-updates (9.0.115.0). AS3 was up to 10 times faster than its predecessor