Sorry to hear that others don't seem to be having much joy with their Windows 10 upgrades. Not to rub it in in any way, but I've just finished my 2nd successful upgrade - this time on my desktop machine. Took all of 20 minutes from start to done. OS on SSD FTW!
This time round I did have one warning ! in Device Manager on restart - the GeForce Windows 10 Nvidia drivers for the GTX970 did not kick in until I rebooted once. After that, all seems good. Unfortunately game testing that I was hoping to do this evening will have to hold on until after Escum have had their way with my electricity tonight, but hopefully will be able to check a couple of titles then.
I did spend most of today working on the laptop I upgraded this morning, and picked up zero issues at all. Didn't have too much time to check out new apps and features, but work and office stuff was all working perfectly. (knock on wood!)
Right now, I'm a happy camper. Best Microsoft upgrade experience I've ever had by far. Hope others wanting to upgrade get theirs soon too.