I have now updated my main photographic work system to Windows 10 and it’s working OK.
There was a heart-stopping moment where we had a power-cut whilst I was in the middle of the installation, but when the machine restarted after the power came back on three and a half hours later (thanks Western Digital) it rolled back everything to Windows 7, so I had to start the W10 installation again. This time the installation went without a hitch.
The only problem I had with the completed new OS was that the Spyder 5 monitor calibration .icc file didn’t load properly and refused to do so without turning the screen a rather nasty dirty mustard colour. So I recalibrated with Spyder 5 and created a new .icc file which is now working fine.
So for me, the transition to Windows 10 wasn’t too bad at all.
The other thing to remember is that performing the update means that W10 has now written over the W7 serial number, so if you want to do a clean installation from media in the future, you will need to enter a W10 serial number to activate Windows. You can obtain this number by using a serial recovery utility after you have initially upgraded to W10. I have used Produkey with no problems.