Only weeks ago, AMD released the first update to its Catalyst Driver package in over six months, but that didn't stop the company from updating the Catalyst drivers for the retail release of Windows 10. Catalyst 15.7.1 contains Catalyst Display driver 15.20.1062 for Windows 7 and 8.1, and Catalyst Display Driver 15.20.1062.1002 for Windows 10.
Version 15.20.1062.1002 has full support for WDDM 2.0 and DirectX 12 on all Graphics Core Next products from AMD. This includes all Radeon HD7000 GPUs and newer, as well as A-series APUs from 7400k and up.
According to the release notes, the new driver fixes a number of known issues, including fixes for Battlefield 4, The Witcher 3, Cyberlink PowerDVD 3D playback and several other general bugs. Along with the fixes come a new set of problems: Some of the new issues include Firefox crashing with two or more tabs open, and AMD suggested opening separate windows as a temporary workaround. There is also an issue with Intel and AMD configurations that cause a blue screen on install. AMD suggested installing the driver through Windows update if this occurs.
Nvidia has also released a new WHQL driver for Windows 10. GeForce driver 353.62 for Windows 10 supports every Nvidia 400 series GPU up through the 900 series, though not all GPUs have full support. Nvidia stated that Fermi-based GPUs (ranging from the 400 series discrete GPUs, through the 500 series and some of the 600 series) do not currently support WDDM 2.0 mode. These cards will run in WDDM 1.3 until an undisclosed later date. All Kepler- and Maxwell-based cores support WDDM 2.0 and DirectX 12. The release notes make no mention of bugs, nor do they specify any fixes.
Nvidia published a support article explaining that Windows 10 will only support one mode at a time, and it will automatically detect which one based on whichever driver loads first. For this reason, it is not currently possible to use a Fermi GPU in the same system as a Kepler or Maxwell. If you use an old graphics card for extra displays, or a dedicated PhysX card, you may want to wait, or you'll be forced to give it up temporarily.
Nvidia doesn't make any mention of this on the website, but one of our contributors has already received his free update for Windows 10. He confirmed that the driver that Windows update installed automatically matched the version available from the website, so you likely don't have to worry about doing it yourself.