Agreed to use this at ATL a few days ago.
There are separate lines for Pre, Pre Touchless, and Pre+Clear. Asked the guy at the end of the (very long!) Clear line which would be faster and he pointed to the Pre Touchless line. However, he was far from right. The Pre line was around the same length as the Pre Touchless line - but moving about 10 times faster due to having multiple desks open rather than just 1 for touchless. After a bout 5 minutes (with maybe another 10+ still to go) I jumped the line over to the normal Pre line, and was through in about 2 minutes.
If TSA are expecting this to be a useful thing, they need to provision/staff it correctly - which certainly wasn't happening at ATL when I was there!