Hi Hammer,
I've used one quite a bit, as a matter of fact I invented it. I've used 1907 style slings for years and found that they had a few drawbacks-
I wanted a sling that was made for hunting, not shooting matches.
One drawback was weight, 1907's are considerably heavier than other slings. The second was speed. separating the straps, especially in the prone position can be difficult.
The Pronghorn weighs less than half of what a traditional 1907 sling does. The integrated loop is quicker & easier to access in some field shooting positions.
I've used hasty slings and found them less than ideal. The fact that the strap is continuous will make the rifle want to roll in your hands as the strap contacts your mid-section, introducing a torqueing effect. You must use your hands to counter act this rotation while trying to aim the rifle. On weaker stocks, this side pressure can cause the forearm to contact the barrel.
The Pronghorn's lower strap is attached to the bottom of the arm loop and is free to traverse the loop- ie. it will swing out of the way, preventing contact with your mid-section which eliminates the rolling effect.
You can get this same rolling/torqueing effect with a 1907 in certain shooting positions if you don't unhook the rear swivel, which is time consuming and not something you want to be doing when trying to take a shot in the field.
With the Pronghorn, you don't have competing forces to deal with while aiming, just the desired tension between the back of your arm and supporting hand on the forearm, which is exactly what you want.
Hope this answers some questions and thanks for considering our product. Instructors at Gunsite have found it useful and Mr. Wayne van Zwoll is a fan as well, so we must be doing something right.
Regards,