I too was a diehard Win7 user and fan. This is my upgrade story.
Back when the first free W10 upgrade period was available, I did upgrade my old Toshiba laptop to win10, just to play with. That was the W10 home version and I didn't like it. Some things like Mail and Edge were hopeless and it seemed to be designed for touch screens. Anyway, I hardly used it. Later, my wife's computer died, so I gave her this spare. It is quite an old Toshiba with only 4Gb and has an Athlon processor. Not long after I gave it to her, a Windows update killed it (and other computers that used that processor)! It was a month or two before MS issued an update that did not kill Athlon computers. Since then, it has worked fine for her.
For my own Lenovo, I was more cautious. I cloned my Win7 Pro to a spare drive and removed it. Then did a W10 upgrade to existing drive. I forget the details, but I ran into problems that I could not resolve. Eventually did clean W10 install. Other than some testing never used it. It was on an SSD, which was a waste, so eventually I cleaned it and used it on my wife's computer. So now I only had Win7 on Lenovo.
Over the holidays, with upcoming demise of Win7 support, I decided that maybe I should again try Win10. I again cloned my Win7 and put it aside. Then did an upgrade to Win10 (No problem with licence because I had done this when upgrade as free). Then I put the Win7 drive back in and was able to dual boot from BIOS.
Ran into some minor blips, but not much. I hate to admit it, but I have now chosen Win10 as my main OS

It seems to boot up faster and so far I have not been able to find anything else to complain about

Everything works as before and I like the fact that Defender now provides solid protection. I have not moved my Malwarebytes premium licence over yet, because it is needed on Win7 until I have to abandon my trusty old OS