Playing with Prime is still a non-hacker experience for me and I didn't encounter any blatant cheaters. Although there could still be cheaters using unnoticable hacks.
I think making the game free to play will keep hackers seperated from Prime players. Hackers used to buy cs to cheat because it was "Fun" for them, as explained by the cheater in 3kliksphilip's video. So now hackers just have to make new accounts to cheat which is way simpler for them, and they won't spend money to get Prime unless they want to be absolute dickheads.
So basically you still have to pay for prime if you want to actually play fair CS.