This morning I pulled out one of my old USB 2.0 external HDD's, and formatted it, to not only make a system image from my system disk, but also of my 2nd internal disk that's used for Libraries and backup images and File History.
The time is nearing for Win10 RTM and if something goes wrong I want to be prepared. My system is working perfectly(no problems after the last round of updates & patches), all my software/programs are up to date, and I have disabled my installed theme and run SFC-DISM to reset everything.
This is taking a while because I'm making an image of 11 Reflect system images too on the backup partition.
I cannot recommend strongly enough, that everybody else do this(especially the ´"beginners") or else here in the forums there will be a lot of "I lost all my files, what do I do now?" posts, when there is a power fluctuation or you lose internet connection or maybe be a driver/software(in my case it was Samsung Rapid) compatibility problem that causes a BSOD after Upgrading.
So prepare right now for the worst if your system is running smoothly and do yourself a favor and image all your internal disks now, even if you do a "Clean Install", because you never know....