My "workplace" experience with the single-point sling confirms what everyone here has already said.
I love ATAS, I'm stealing that.
But in all seriousness, the jewels did not like the single point sling. For a flat range environment doing drills, it works great, but for moving and shooting, there is nothing better than the quick-adjust two-point. I have personally used the Vickers sling, and I know a lot of guys who use a VTAC, they seem about the same in function.