"Good day, Windows customer. Your mission, should you decide to accept it is to test Windows 10. As always, should you or any of your shadow users be caught or killed, Microsoft will disavow any knowledge of your actions. Your previous OS will self-destruct in 30 days. Good luck."
As I wrote yesterday in Windows 10 is Turning Me Back into a Windows 7 User, Windows 10 is a mish-mash of Windows 7 and Windows 8 features – but in this humble writer's opinion, the scales are tipped more in favor of Windows 7 users. And, it makes sense, since Windows 8/8.1 had never been able to find favor with customers, leaving the majority of the Windows market using Windows 7. To bring Windows 7 users forward into this decade and keep them from being tempted to seek out Windows replacements, Microsoft needed something capable of hitting the mark for PC users. Welcome to Windows 10.
Those that upgrade from Windows 7 fall in love almost instantly. Those that come from Windows 8/8.1 feel like something's missing. And, there is. Windows 10 is a fantastic experience for a keyboard and mouse, ensuring that Windows 7 users can have a semi-seamless familiarity from day 1 of the upgrade, but, even with Windows 10's new auto-switching capable tablet mode, the tablet experience needs work. And, I'm positive we'll see gains in this area in the short term, as Windows 10 receives minor updates over time and then a big set of new features in the September to October time frame.
And, this brings up an important point. If you're not happy with Windows 10 now, you can still roll back to your previous operating system – but, under two conditions:
You decide to rollback within 30 days of the upgrade.
You performed the upgrade method instead of choosing to do a clean install.
During the upgrade process, your old Windows instance is stored on the PC, allowing you to roll back should Windows 10 not fit your fancy. Windows 10 will store these files, but only for 30 days after the upgrade is complete. Once that 30 day limit is reached, Windows 10 will remove the ability to roll back, also removing the files necessary to perform the action. Windows 10 is sort of a try-before-you-buy deal.
If you chose to do a clean installation of Windows 10, instead of using the upgrade method, the ability to roll back is not an option. To get back your previous version of Windows, you'll need to install the old OS from scratch using media and your old OS key.
Using either method, though, Microsoft stores your Windows 10 license in the Cloud so you can always install later on, on the same PC, without having to obtain a new license.
If you decide within the 30 days to roll back, you can find the option in All Settings > Update & Security > Recovery.