Atlantico: Only catch is... what he says is not true. Anyone can downgrade from Windows 10 to whatever Windows version they upgraded from until the end-of-life for that OS. So until 2020 for Windows 7.
Goddammit people, stop with this internet voodoo advice. "I heard it on teh intarwebs so it must be true!!!111!"
Microsoft states otherwise:
"Yes, while we think you will love all the features of Windows 10, you will have one month after upgrading to revert back to the previous version of Windows on your device."
That's directly from Microsoft's FAQ about the upgrade.
Also, I just came across this:
"If something major happens to the device that requires something as monumental such as a motherboard change (basically turning it into a new computer), Windows 10 will require re-activation – which will require you to purchase a license. This is what Microsoft means when it says "life of the device." Additionally, you can't transfer a license to a new device."
I've read something similar to this from multiple sources now. So, what this means is that, if I wanted to upgrade, I would turn all five of my expensive, full versions of Windows 7 & 8.1 Pro into Windows 10 Pro OEM copies.
That's a massive no-thank-you from me. Since that's the case, I'll be passing on Windows 10 indefinitely.