Well as many will know about poor HD flash as it has traditionally only used the CPU. 10.1 hopes to rectify this with GPU offloading.
So this is just a heads up to those who want to have a play and have a supported GPU (the list of supported ones are in the release notes)
Just to remind people this is a BETA so may well be buggy.
If all the above makes no sense to you just wait for the full product release.
Link in 1st post.