I've been doing fine with my 7870 on all drivers, latest one being some earlier beta revision of 13.11.
Then today I installed 14.1 beta for Mantle, and I quickly noticed this taskbar flickering on Win7 x64 SP1. It showed up for me when I was (softly, 80% GPU or so) running a litecoin miner and viewing GPU-heavy sites in latest Chrome browser (like youtube, twitter). The windows taskbar starts getting freaky. Looks like memory corruption, starts small and spreads fast. At first there's a single ~5x5px square flickering with an invalid texture, but within seconds other squares follow. These squares aren't all next to each other, and tend to be more on the right side of the taskbar. This corruption is repeatable after every fresh restart.
I downgraded to 13.12 WHQL, which should be the same driver that 13.11 beta was. Thus far 13.12 has been working flawlessly, just as 13.11 did for months. So definitely looks like 14.1 changed something that causes what looks like memory corruption.