I just updated my game to 1.10 via GOG Galaxy and when I try to start the game all I get is black screen and nothing else.
frame rate and "recording" icon from my ShadowPlay is displayed but no sound, no menu, nothing, just black screen.

Windows 10 Pro
i5-2500K @3,60Ghz
16GB RAM
GF GTX 780 (358.50 driver)

I had no problems prior to installing the last patch.

Same here. I turned off geforce experience and still get a black screen that then collapses to the task bar.
I'm going to try to roll back to the previous patch via galaxy and try to re-patch.

I was hoping I can avoid reinstalling the game but well.
I rolled back to patch 8 and game was running OK.
Still I see there is a lot of performance issues with the latest patch so I'll just wait for some hotfix if not I'll reinstall the game...

Looks like I'll have to try that as nothing else has worked. I've backed up my saves but am wondering whether to start from scratch.
Good to hear this fixes it though :-)

Update and solution for anyone else who might have this problem.

I deleted and re-installed the Witcher 3 and it ran fine until I loaded the Nvidia (geforce experience) game optimizations, at which point it did the black screen behavior. Reverting to its un-optimized state allowed it to run perfectly. It looks like the Geforce settings can't cope with the latest patch.