Win 7 was my favorite so far by a long shot. Fastest and best working version I have ever had. Skipped all the Win 8 versions. Win 10 is fine here as far as everything working. The Edge browser leaves a LOT to be desired. The menus and Win screens in 10 are pretty ugly too, but I have had no operating problems with the Win 10 itself. Have it on 2 computers, both home built and a little over a year old, we upgraded last year. My older PC is still awaiting the Win 10 update. Applied for it, but they haven't said it's ready yet. That PC is probably 5 years old, maybe a little more? I am suspecting they may have detected some compatibility problems because the other two PC's had the Win 10 updates ready to install as soon as I applied for them.
The only reason I went to 10 is because it was free. Didn't want to have Win 7 end up no longer supported and have to PAY for 3 more copies of Windows. After seeing 10, I suspect many large corporate users will stay with 7 and it's expiration may be extended like XP was? Don't know if they get a free upgrade to 10 or not, but they could also be wanting to take advantage of that if it is free. Costs some of them a TON of money to upgrade entire companies.
