The only glitch I've found is Adobe Acrobat
It might be because WIN10 comes with it's own PDF printer that is now installed, I have AcroBat Pro and it still works, ALTHOUGH I might of had to make that the default AFTER the upgrade?
Overall WIN10 seems OK and most importantly it didn't break much during the install, in fact older printers I feared wouldn't work still work fine. I do have some old apps written in the XP or previous era that won't run, BUT they didn't work on WIN7 64 either. NO XP mode for WIN10, still working on a fix for that, it turns out you can install XP via Hyper-V if your hardware and version of WIN10 supports it. I installed yesterday and it works, I just haven't figured out the integration with the host (WIN10) yet for moving data back and forth.
I do NOT like the new browser, so un-defaulted that, I have a software that writes HTML files that it won't open, probably written to an older IE version standards. Also despite the claims for faster, etc., it seems slower, not many features and it won't support Microsoft Silverlight which a lot of web sites still use, it may be more secure and modern, but without backward compatibility it isn't ready for prime time. Out of IE, EDGE and Chrome, Chrome seems to still be my favorite for speed and ease of use, BUT still need to use IE for some things.
Haven't migrated to the built in e-mail app within WIN10.
Quite a few things I haven't figured out how to tweak yet either, maybe over time, for now it works and I am being more or less productive with WIN10, wasn't a disaster, but wasn't earth shattering improvements that I can see over WIN7 either.
TS