I've been using Aptitude Products for about a year now. Not once have I been suspected by players, the games anti-cheat or the developers themselves of cheating. I've been using R6: Absolute for the last week and I thought I'd leave some of my initial impression.
The Good:
The program itself could not be any simpler. Simply run the app and the recoil is automatically adjusted for you regardless the of gun you are using.
The adjustment this makes to the weapons recoil radically improves the accuracy regardless wether or not you are firing single shoots or spraying in auto.