I have M16 sling on my M590DA1. Its simple, cheap, and effective. I tried a 3-point sling on it, but I felt it was no good, as I tried grabbing for a pistol grip that was not there, as if it was a M16. I have a single point sling on my SBR'ed (10.3") AR that works great for that.
They are both great. The dual point for long periods of carry like when out in the west desert shooting rabbits. The dual point get used alot more but the HK clip loop on the 870p and the M590A1, was only 30, and I have a few singlepoints with HK attachments so I figured "why not" and got them.