I guess it’s important to note that both operations - the upgrade and the rollback - are not entirely without risk. Either one could go wrong, potentially quite catastrophically. IMO this is a banal truth as the risk is small, and is present with any kind of major upgrade on any platform.
In terms of advice about whether you should upgrade or not, I’ll need to talk about Win8.x first…
What was improved in Win8:
[li]The OS (Kernel, memory management, permissions management) was a bit more stable and functional than in previous versions[/li][li]There were some good improvements to minor things like the file copy dialog, file history (sort of a file backup mechanism)[/li][li]It typically ran faster than Windows 7 on the same hardware due in part to ‘flattening’ of the visual elements (removal of the ‘aero glass’ stuff)[/li][/ul]
What people didn’t like in Win8:
[li]Loss of the Start Menu. I didn’t care, but I think Microsoft really badly misjudged the public reaction to this. The (tiled) Start screen was in some ways a usable alternative, but removal of the actual Start Menu took away some features (jump lists for example) that people like, without offering any alternative.[/li][li]The Start Screen itself - Many people took one look at the new ‘Metro’ tiled Start screen and turned away right there and then. It led to (IMO incorrect) views that Win8 could only be used properly with a touchscreen and (provably incorrect) views that the Win32/desktop application environment was dead and gone.[/li][li]The dumbing down of control panel type screens - in order to be more touch-friendly, many of the control panel applets for system settings were hidden away and replaced by touch-enabled Metro apps, but this was done quite clumsily and some features were a pain in the ass to configure. One of the major changes in the Win8.1 update was to give back the traditional control panel stuff.[/li][/ul]
What’s new in Windows 10
[li]The Start Menu is back, and is a bit better than it was in Windows 7.[/li][li]The tiled Start screen is now a sidebar on the start menu (in desktop mode) and the tiles support jump lists (best of both worlds)[/li][li]There is a distinct ‘tablet mode’ that favours touchscreen modes of operation.[/li][li]Some of the touch-friendly user-friendly control panel stuff is back, but works better this time.[/li][/ul]
What’s different in Windows 10 (that you might not like)
[li]Updates can’t easily be postponed forever in the ‘home’ versions of the OS.[/li][li]The choice of colours in the theming engine is sort of limited. [/li][li]The user-friendly versions of the Control Panel applets may create a sense of unease (they work fine, but as they look less ‘technical’, they could make you feel like you have less control)[/li][/ul]
My overall view: I upgraded my Win8.1 machine to Windows 10 and I think it’s OK. I like the new Start Menu, but I sort of miss the Win8 Start screen too. I haven’t had any problems with hardware or software.
I also recently bought a Windows 10 tablet and I will be honest here: Windows 10 is not as good a tablet OS as iOS or Android. It has the advantage of being able to run full-blown Windows desktop apps (so it could potentially completely replace a laptop), but because it’s a desktop OS worked over to run on tablets, it’s still a bit clunky in places - in particular, the integration of the touchscreen keyboard - it doesn’t always appear when you want it; it doesn’t always disappear when you’re done with it, and when it does appear, it very often obscures the place you’re trying to enter text into.
Should you upgrade? Check for compatibility of your printer and your important applications first (Google “[whatever it is] not working in Windows 10” and see if you find people reporting a problem with something that is critical to you.
If you like Windows 7, you’re going to be OK with Windows 10, but if you’re perfectly happy with Windows 7 (and especially if you plan to replace your machine before Windows 7’s End Of Life), there might not be any hugely compelling reason for you to upgrade.