i got the contractor pack and i'm still doing my evaluation of the sling. so far, the downsides are:
1) i don't like the 2 point sling configuration. the sling is too busy w/ too many buckles. a 2 point sling needs to be smooth to slide easily off your shoulder in either african or american carry methods. i don't think it is a good 2 point sling.
2) b/c of the additional QD buckle, the single point rides a little low. although this does help in transitioning from left to right.
3) you can't really go from one sling set up to another very quickly or from one gun to anther quickly. it takes time to properly set up the sling. maybe this was just my preconceived notion, but ithought one could just from a 1 single point to a 2 point w/ just a few snaps, but it acutally takes some reconfiguring. also, you can't go froma 3 point on an CAR to a 3 point on a shotgun w/out some modification. it does work however going from single point on a CAR to a sling point on a shotgun w/ out any modifications, provided you already have the weapon attachments already on teh guns. this could prove to be very useful in 3 gun or actual combat.
but as i said i'm still not finished testing. these are just my preliminary thoughts