I've seen a couple say it's okay,but none as yet say it wasn't.

What problems are you having?

Did you just do the upgrade or a clean install after your free upgrade?
Have you updated your graphic drivers?
Did you get some kind of error message?
What kind of problems do you have?

I did the free upgrade to Windows 10, then tried to run the game. I pressed "Continue" and it tried to load my last save but the screen was extremely dark. No commands worked e.g. Esc, W, no mouse cursor. Geralt moved jerkily every 5 secs or so. I had to do Ctrl, Alt, Del to get out of it. No error message. Haven't done any manual update of the graphics = don't know how to...

Not me.
I'm running The Witcher 3 in Windows 10 right now, and it doesn't seem to behave differently from how it did in Windows 8.1. I recommend you update your graphics drivers.
I had to update mine for my GTX 980, because Windows 10 didn't behave at all. Only 1 screen out of 3 was working, and the resolution was a complete mess.

No problems after updating the drivers and rebooting, though.

I had the same problem but found this and it helped me at least [url=]https://youtu.be/fnPtUbKVB5Y[/url]

mine works even better! new Nvidia drivers too for w10, just don't install that crappy geforce Experience

I would recommend to try to update your graphic driver. For a NVIDIA card go here:
http://www.nvidia.co.uk/Download/index.aspx?lang=en-uk
For an AMD card go here:
http://support.amd.com/en-us/download

He should check with windows update is there are any more updates to fix.
As soon as I installed Windows 10, my nvidia drivers got shafted and I couldn't even unistall them.
From windows update, windows 10 found a newer version of the drivers (which is false, it was the same version I installed yesterday night) and some other system updates.

Windows Update failed installing this allegedly newer version of the nvidia driver and installed the other fixes.
After that I restarted the pc and suddenly my second monitor got recognized again, nvidia experience started working again, and the drivers were OK without reinstalling them.

Managed to solve my problems. Nvidia hadn't updated my drivers as the win10 update had corrupted my Java and I had to reinstall it. Once I'd done that the new driver for the GTX 980 was downloaded and the game worked again.
Thanks to all the people who tried to help.

Nice! Have fun again with your game!

I just did the 10 upgrade this morning. Started up and all my saves were gone. Luckily I made a copy before upgrading. Copy pasted my saves and everything seems to be ok. Only ran around and then saved to check if that worked but stutter I developed at level 27 seems to be gone. Hopefully forever.

Did a clean wipe before installing 10.

Haven't noticed any difference in performance. Running great, as usual.

Of course I backed up my documents folder, among other things, to an external drive prior to wiping.

I've had a similar issue. No videos are playing (no legal text on startup, no startup video) and when I hit continue the game just does not load (along with no intro video). I'm on the latest Nvidia drivers, and I can not figure out what is wrong. I've tried a clean install, restart, etc, and it just does not work on windows 10 for me.