Just thought I would share my experience changing over to Win10 from 8.1.
Installation went OK. First issue was XLN having to add my computer ID again. Went through that OK. Unlike a previous poster, Win10 was in the drop down menu, and once added, all good.
Then I installed the new beta driver from Focusrite for my 18i20, and the fun began.
Audio was extremely bad. Sounded terrible and full of clicks and pops. Did all the usual parameter changes but nothing worked. Uninstalled and re-installed the old driver. Same. Two hours of mucking around, trying again with the new driver, different interface settings. Heaps of re-boots, turn off everything available not necessary in WIN10 options. Nothing worked, except the very last thing I did, which was re-install the old driver, for about the 4th time, and changed the midi playback buffer size, again, and suddenly everything worked, but I swear, I had done that a few times already.
So no idea, but when I shut down last night, it was working, and I will get back to it again tonight to double check all is well, as I need to kick off a new customer project.
I expected driver problems I guess, but it's still frustrating, particularly not really knowing what the issue was. I havn't tried keyboards yet...........