I'm having some serious issues after upgrading to 15.7 (both on windows 10 and windows 8.1). The problem is a bit hard to explain, and sadly can't be screenshot'd (I will upload some videos later on). What I see are horizontal, black lines across all my monitors, happening when I don't run any game at all. Like if the video signal got corrupted somehow. It seems that if the gpu has enough work to do I don't have the problems (running a full screen youtube video / playing a game greatly decreases the occurrence of the glitches). Disabling crossfire didn't help. Removing the drivers and reinstalling them didn't help either. Games run fine without issues.
If I switch back to a driver earlier than 15.7, I don't have get the glitches anymore. (sadly, that's proving to be a hard one after upgrading to win 10) The same thing happens if I disconnect one of the monitors using dvi-d. Since going back to an earlier driver solved the problems on windows 8.1, I think we can rule out the hardware issues.
My config is the following :
2 x R9 290X Sapphire Tri-x
3 x Dell 27" running at 2560x1440, one using displayport, two using dvi-d.
990fx / Crosshair V Formula-Z
15.8 beta driver