In my pre-end-July batch of computer updates from Windows 7 Pro and Home, 32-bit and 64-bit, desktop and laptop, I have had mixed results:

a) two machines, a Medion desktop and a Dell Optiplex 755, had no problems in updating (apart from having to revert to UK in both language and date/time format...)

b) three machines (Dell Optiplex 760, Lenovo Thinkpad T520, Toshiba Tecra A10) had various errors, which required

* removing a Cisco VPN virtual adapter before the upgrade process would begin in one instance

* deleting several files on another

* obtaining "Page fault in nonpaged area - pssnap.sys" when restarting Windows 10.
This took me 1 days to resolve, after doing a CHKDSK of the C: drive and running Memory Diagnostics all night, both without problems, some Googling mentioned about removing Macrium Reflect Free. I had Macrium Reflect Professional on that Toshiba Tecra A10 laptop, but removed it anyway, and this proved to be the critical factor. Windows 10 then installed successfully. I haven't yet reinstalled Reflect.

I was particularly impressed with the automatic reversion to Windows 7 on the Toshiba laptop (several times!) when the pssnap error recurred.

On the whole, the upgrade process was ultimately successful, but disappointingly messy, which took a long time. Once you unpin all the tiles from the Start menu and move the boundary left, and do a small amount of additional tweaks, it ends up almost the same as Windows 7!