I'm planning on upgrading tomorrow. I'll post here how it goes. I also created the same kind of thread on BleepingComputer so users can share their experience with the upgrade and let us know if they experienced any issues and if they did, how they ended up fixing them. I'm sure this will help a few users.
Personally I'm sure my upgrade will be just fine. I don't even have a third-party Antivirus right now (I uninstalled KIS to get Hyper-V working), I use Windows Defender on Windows 8.1. So this is one program that could have caused an issue. I'm running NVIDIA drivers from 2-3 months ago, so I shouldn't encounter the latest issue with Windows 10 and the newest drivers. The only worry I have is that I have both SQL Server and Visual Studio installed, so I don't know how they'll react to the upgrade, but I'll test them right away once I get on Windows 10. Other than that, I don't have any personal data on my SSD (where Windows is), everything's on my HDD so I won't back-up my data for the upgrade since my HDDs will remain untouched.
That's it for now I guess.
