Someone remind me in 5 days to not install Windows 10.
I love my DualShock 4 too much to game without it.
You'll get prompted to download it so you've got enough time to back out. Also if you did there's nothing stopping you going back to 7/8.1 as all that happens is your licence, ie your product key, is granted Win 10 privileges (that's either a copy of Win7/8.1 or 10 installed on a PC at a time but not both). It's not eaten, you don't lose access to your old version of Windows and despite the Digital River hosted iso's not existing anymore Microsoft does have a Product Recovery site to download the applicable version (although can be a little wonkey with OEM Product Keys so I'd check first). There are way more advantages upgrading to Win 10 for me than to be bothered about lack of one type of 3rd party controller support but hey each to their own.