Then get Debian or Fedora. I'm serious, if the OS is doing things so bad you're willing to execute untrusted code with elevated privileges to modify the OS, you've already lost.
Everything in that script is straightforward and if not easily googled to determine what its doing. It's not black magic.
But I have to question your attitude, especially here on a forum called "Hacker News"; why do you advocate against exercising ownership over one's rightful property? Microsoft already got their money and they should leave users the hell alone. There is a proud history of hacking one's PC and poking big brother in the eye, don't forget that!
I walked up to my laptop and in the upper-left corner of the screen Cortana wants me to try ordering Star Wars tickets. Fuck you Cortana, don't tell me what to do!!!!
I do agree that people executing this script should not only rely on "it's open source, so smart people will look at it and find issues", but actually research and fully understand what is going on.
I have a bit of a pet peeve about the word "untrusted", because it leaves open who is doing the trusting.