Coming back to my early reply in the thread
I have now taken the plunge of installing Windows 10.
Linux is still, somewhat sadly, not an option for me, yet. I play too many games and have to use Windows at work.
A couple of observations, after one day of using Windows 10 (1809):
First of all, with a slow internet connecting, installing Windows 10 sucks. I have only a 6 MBit/s DSL connection, and downloading updates takes a loooooong time. The stupid thing is that this is a bandwidth hog, taking everything it can get, no matter that other active processes are currently using bandwidth. A running download for example was throttled down to single digit kBytes/s... I hope this calms down in the next couple of days where I just leave the PC on over day.
The UI seems to be slightly bigger. Especially the Taskbar set to two-rows is obviously larger than under Windows 7, but I think the titlebar is also bigger. The scaling is set to 125% (same as I had it under 7), I have noticeably less screen space than before.
To disable Telemetry as far as I can, and get rid of unwanted features, I used O&O Shutup 10, a small portable executable. This cannot fully disable Telemetry, but reduces it to a minimum without you having to fiddle around in dozens of menus. It can also get rid of various features, like bing connected search or Cortana as far as possible.
I also disabled Hibernation and Fast Boot. Hibernation wastes 32GB of disk space in my case, and Fast Boot can wreck dual-boot machines. And even with Fast Boot disabled, the box boots somewhat faster that Windows 7 did.
There is still some tweaking to do, I am sure of it. But so far it seems to work, and most obvious annoyances are disabled. Let's see how it will behave after the update to 1909.
All in all it took me an evening to install (including a thorough physical cleaning of the computer) and another evening to get the first stuff restored from backup and up an running again. Updates are hopefully completing today. I have to admit: that was faster than I expected. This time also includes two curveballs I encountered: My QNAP NAS was still using an old firmware supporting SMB1 only, and Windows 10 would not connect. So that took an hour to update as well. And it seems my big internal storage harddisk is about to die...
Oh, and I used my Windows 7 Ultimate key during installation, so that still works.