I had a 17" MacBook Pro Early 2011. It was running only Windows 7 and bootcamp 5. I had removed the Mac OS entirely because I had many specialized programs that required windows and so didn't use the Mac side much. In this special case I did not have access to bootcamp assistant to download the new drivers and windows update no longer updates bootcamp directly there so I was stuck with bootcamp 5.
Windows 10 upgrade said the computer was compatible except for the Bluetooth controller. Performed the upgrade from Windows 7 directly and it went smoothly but bootcamp is not longer in a layer between the OS and hardware so I have lost: (1) Volume up/down/mute, (2) brightness up/down, (3) bluetooth (as expected). I did not lose Wifi (which I was nervous about because it is on the same expansion board as the bluetooth module).
In general I am happy with this decision. In the future I might try to find someone with my mac to help me restore the bootcamp features. But I can live without those.
Windows 10 is perfectly worth the effort and look and feels just like my old 7 mostly. So I am very happy except for the few items listed above. Hoping for another 5 years out of this machine.
Best Wishes,
Bradiko