I'm using the fbdev frame buffer driver in X. I find I get better performance with it than I would with armsoc. You could proceed down the road to getting the mali dri driver up and running, if you like but I'm not sure that would add anything to 2D or video decoding. You'd just pick up OpenGL ES and OpenCL.
The most complete directions I saw for Mali on the Samsung/HP Chromebooks were here:
http://malideveloper.arm.com/develop-fo ... hromebook/ but when I tried to implement their patches I couldn't even get the 3.8 branch to build. I figured it wasn't worth it. The video acceleration stuff is based on OpenMAX I gather but I don't believe the open implementations of OpenMAX support. Using the fbdev driver, the main CPU is fast enough to play 720p h.264 video. Everything else with that seems to work fine, other than if the screen blanks it never wakes back up again.
I haven't had the wifi drop out issue. I do however have uBoot forgetting what it's supposed to do every time I boot the machine. I have to type in run non_verified_boot and it boots up fine but it has a few marbles loose.
It's still a very fun machine