I'm with you guys and I'm tired of fighting with it as well. I now took a video of the issue and posted it on another forum as well with hopes someone may have a solution. I thought for sure that the 9.12 drivers would eliminate this problem. Then I started to think that maybe it was just me. I hear all about the other tearing issues with overclocking on the desktop, but no one really addressed the refresh issue even with no overclocking.
http://www.youtube.com/watch?v=saG2mr6qM_8
My problem persisted with either the DP adaptor or native DP connection, so more than likely its a driver issue. I know the 4870x2 had issues when it first came out, and most were fixed within the first 2 months of release. So far owning both 5870 and 5970, I'm starting to pull out whatever hair I have left.