If you are using a notebook, you might want to postpone the Windows 10 upgrade though until the GPU vendors fully caught up: Currently, the Heavensward Benchmark crashes on my machine (NVidia Quadro K3100M) immediately when choosing DirectX 11. DirectX 9 works fine, though. No problems on Windows 8.1.

I am sure the problem will be gone by the time W10 is released, but you really want to make a full backup / hard disk image of your computer before upgrading, so that in case something does get screwed up, you have a way back.