So I finally took the plunge and upgraded to Windows 10
And it's actually alright.
Bought a Windows 10 Pro key from
Amazon for £30. Downloaded the
Windows 10 ISO from Microsoft's website and copied it to a bootable USB drive. Restarted PC, booted onto the USB, ran the installer, and performed a clean install. Overall it was pretty painless and not as big a hassle as I thought it would be.
Btw if you're currently on Windows 7 or 8, the free upgrade to Windows 10 ends on
29 July. After that I'm not sure if there'll still be any cheap keys around, and cracking W10 seems to be much harder than 7 or 8. Honestly I would just spend the £30 now and upgrade, save the hassle.
If you're gonna buy the same key I bought from Amazon, make sure you do it quick as the key is delivered to you via post. I'm pretty sure these keys are just unused Windows 8 keys (which will still allow you activate W10, but not after 29 July), so I wouldn't hang around.

Start menu is miles better than the one from Windows 8. I even prefer this one over Windows 7. We'll ignore that Candy Crush tile...

Searching from the start menu is also nice (just press Windows key and start typing).
Interface is clean and spacious. Everything is snappy and just works. Also good to know I'll have DirectX 12 now, so I'm future-proofed for that.
Glad I did the upgrade, it's not as bad as I thought it'd be.
P.S
If you're gonna upgrade, it's recommended you do a clean install (i.e. formatting your hard drive/SSD, and then installing). Originally I tried to do the upgrade procedure from W8 to 10, but had some issues.