Just to present a positive experience, so far I haven't had any problems with Win10.
I held out using Vista which worked okay (believe it or not) except the old tower was taking around four minutes to boot up and a lengthy time to shut down!
After Microsoft decided to stop supporting Vista at the same time as XP (grrrr) I decided to get a new PC about eight months ago, a Lenovo Tiny M700, which had Win10 pre-installed. I specified a solid state drive, which I assumed would speed up the operating system, as well as 16GB of RAM which might help with video editing and electrical simulations which are fairly intensive.
On the new machine most updates have only taken a few seconds. There was a major one about three or four weeks ago which warned it would take some time (an hour or two from memory) and there would be multiple restarts, but it was all over in about ten or fifteen minutes.
My user files are all intact, although I never let an operating system decide where it's going to store any of my personal data. I set up my own directories and back them up separately from the operating system, so I just copied them from the Vista machine to the Win10 one.
What's the reason it's all going okay? I don't know. Perhaps a clean install rather than an upgrade from Win7 etc. Perhaps having it pre-installed. It shouldn't matter but you can bet Microsoft is making sure everything works on the new machines from the big hardware vendors. Using a late model processor? ( i5-6500T 64 bit in my case).
Whatever happens, the SSD drive ensures it will happen faster lol. If anyone doesn't want to spend the extra money on a large SSD a good solution is to run the operating system on a small one and use a big disk drive for data.
