The AMD website now offers new version 16.5.1 non-WHQL drivers for AMD graphics cards. These promise up to a 27% performance increase in Forza Motorsport 6: Apex compared to running the game on an AMD Radeon R9 Fury X using their version 16.4.2 drivers. They also note a number of outstanding issues, though it's not clear if these are also present in previous drivers. Thanks Mashiki.