Okay. I got some time to do a simple test of 10.1 vs. 10.2 of Flash and I am happy to announce that yes, 10.2 uses 66% less CPU on average when playing videos.
I tested it with a 720p video on YouTube of IGN's Donkey Kong Country Returns review.
http://www.youtube.com/watch?v=ctijgmv_G3k
With 10.1 I was using about 60% on average of my CPU when in the "larger" video size. With 10.2 I was using only about 20% CPU.
I switched back and forth a few times and got the same results. For all intents and purposes, Flash 10.2 beta is much better with HD video or video in general than 10.1 is.
I am on a 13" MacBook Pro (2010) with a NVIDIA GeForce 320M (256MB). Granted I also have 8GB RAM and a 128GB SSD, but that shouldn't affect the Flash video.