With actual GPU-accelerated H.264 decoding I’m guessing those CPU utilization numbers could drop to a remotely reasonable value. But it’s up to Apple to expose the appropriate hooks to allow Adobe to (eventually) enable that functionality.
Linus won't let Adobe make a decent Flash plugin for Linux. Linus restricts APIs that the plugin needs to run well--things like access to hardware video acceleration.
http://www.anandtech.com/video/showdoc.aspx?i=3678&p=5
See this Adobe PDF for an explanation about Linux: http://labs.adobe.com/technologies/flashplayer10/releasenote...