I'd like to post an update to this thread. After reading all the comments offered on the versatility a sling offers, including increased stability from ALL positions - not just prone - I took the plunge and invested in a Tactical Interventions Quick Cuff Model 2 Military sling. I mounted it to my free-float quad rail tube with a Falcon Industries sling swivel, just forward of the rail cover, which still allows room to attach my bipod or flashlight forward of that without interferance.
I've only been shooting with it one time, but I must say, I really do like it. I keep it adjusted in overall length so I can take up a hasty sling in the standing position or clip in to the cuff and it's properly adjusted for a kneeling position. To adjust for a sitting or prone position requires just a slight tightening of the forward portion of the sling, which is much easier than loosening it. My logic is that a standing position is most time-critical, so a hasty sling should be set up for that position; next is kneeling, so if I've got time to drop a knee, I could probably snap in quickly and be in a tight, slung position. Finally, either the sitting or prone position takes some time to assume, so I figure if I need to get into those positions, I'll have time to make a small adjustment to my sling, too. It's my logic at least
And, to all those who praised the full loop sling, I will say that my groups are already improving substantially - especially in the prone position. I was amazed to watch the sights rise and fall predictably with my breathing, giving me the opportunity to control elevation by holding my breath at a certain point in the breating cycle; this has given me the ability to finally consistently hit a 1" target at 25m, the equivalent of a man at 500m. I've read about this technique but never really understood or experienced it before I started using this sling.
I didn't figure out how to properly adjust it to shoot from the other positions my first trip out, but I think I have now (thanks to some tinkering with it and dry-fire practice), and I feel confident that with a little more practice, it'll move my marksmanship forward across the board.
Finally, being able to quickly "snap in" or "snap out" of the cuff makes this a truly versatile, practical sling that I think is a really useful addition to a gun that is supposed to be a real "fighting rifle."
EDIT - I haven't yet taken the QD single-point sling clip off the stock, but probably will once I get more comfortable with this sling. Until then, it's not hurting anything hanging neatly there on the stock