My experience is that there were tons of cheaters in the middle, most populated ranks, and it cleared up at Global, or at least the cheats were subtle.
I am certain of this because I climbed to global a few times, and I was tracking VAC bans in my game history. In the top ranks, every other game eventually had a player get VAC ban days or weeks later. In the middle ranks it was one or more players every game.
However the cheaters bothered me less than having to play the team's therapist in every game the moment we lost one round!