Adobe CTO Kevin Lynch lays it all out:

Now regarding performance, given identical hardware, Flash Player on Windows has historically been faster than the Mac, and it is for the most part the same code running in Flash for each operating system. We have and continue to invest significant effort to make Mac OS optimizations to close this gap, and Apple has been helpful in working with us on this. Vector graphics rendering in Flash Player 10 now runs almost exactly the same in terms of CPU usage across Mac and Windows, which is due to this work. In Flash Player 10.1 we are moving to Core Animation, which will further reduce CPU usage and we believe will get us to the point where Mac will be faster than Windows for graphics rendering.

Video rendering is an area we are focusing more attention on — for example, today a 480p video on a 1.8 Ghz Mac Mini in Safari uses about 34% of CPU on Mac versus 16% on Windows (running in BootCamp on same hardware). With Flash Player 10.1, we are optimizing video rendering further on the Mac and expect to reduce CPU usage by half, bringing Mac and Windows closer to parity for video.

I still want Flash to go away, but the current debate over it could result in some intermediary benefits. This is coming from Adobe’s CTO and not someone lower in command. Adobe is taking the war on Flash seriously.