If you get that laptop, don't despair. Windows 8.1 has its merits, from the little I've seen of it.

A couple of things - do some research before you set it up. Look (deeply) into privacy settings if you value that sort of thing, and into "telemetry" updates to uninstall. (As I understand it, MS has incorporated some of W10's spyware telemetry software to improve the user experience into W7 and 8 via updates.)

Don't let it con you into logging in with a Microsoft account - set up a local user account for everyday use instead!

I'd be inclined to hang on to W8.1 in case you like any of the programs you get with it, but dual-boot with something like Mint 18. It would be a shame to find, after a while, that you seem to have fallen back into the clutches of something nasty.

Must run. Best of luck with the new machine - looking forward to hearing more!