When i play BF4 the CPU load can be 85% in DX11 but when i use Mantle its the 60% and much smoother and more FPS if i didn't Vsync.
Yea I enjoyed mantle on BF4 it was better latency and smoother for sure and FPS was hugely different for me. I could run 115fps vs 80+ with dx11.
Just better. I am excited with Fury and DX12 as both hardware and a new OS is amazingly fun for me.

stated a 200-400% difference with a engine built for DX12 vs dx11.
Hopefully with the push of 4k and resolution downscaling features now available devs might add this to their games.