I attempted the upgrade last night. Plain vanilla environment.
Windows 8.1 w/ no add on’s. 100% stock. No drivers because no peripherals.
Lenovo laptop. < 2 years old.
Upgrade failed. Restored back to 8.1. Data collected and sent back to Microsoft.
Pathetic.
I did what should be the same as you. LENOVO Flex laptop 4th Gen i5, no unusual software except visio and project in addition to office 2010.
I created an image, kicked off the instalation about 9:15, fell asleep about 10:30 with the install 70% complete. When I got up this morning all I had to do was reboot and log in. So far everything is working.