12.8 works fine for me. Don't know about 13.x as I don't wanna have to clean up the mess if it's worse.
I have used both 13.1 and 13.3 beta 3 and I've not seen any noticeable differences in hash rate. I change drivers mostly on one primary machine and don't often change anything on dedicated miners running stably. Most of my uninstalling and reinstalling to different drivers revisions are from game stability, not sue to mining (good or bad).
Just my experiences. Hope they help...