I don't see any change to the CPU load with the 10 beta. Fans, heat all about the same from what I can see. It is still beta, maybe, maybe the GA code will be different.
I've noticed a 15 to 20% reduction on CPU while playing YouTube videos, and no problems at all.
I'm really hoping they improve more on performance on this version. I know the core shutdown is the actual problem, but 99% of the times I run onto it is while there's some SWF playing -- in fact, to me, the flash player is the main achilles heel of the MBA.