I don't know about a bipod, all of my M4's are setup for 0-300m, not DMR or varmint hunting.
That said, the VTAC 2-point sling is the best sling I've used. The BFG Larry Vickers is a cheap knock-off in comparison (I have both). Single-points are GREAT! for when you're on the gun, but if you need to use your hands or transition, they do not control the rifle at all. It slaps you in the nuts typically, and if you have a can on it, will burn the living crap out of your leg probably, unless you have an SBR, then it will scald your pecker seriously bad. (I don't speak from experience, but rather from common sense seeing where my M4 hangs on a single-point.)
3-point slings are a soup sandwich and you will tie yourself in a knot trying to use them and they don't do anything a good 2 point can't do much simpler. Just avoid them.
This is so far my favorite sling (I don't like LaRue, but this is the cheapest deal, considering it comes with two quality QD swivels already. If you don't need the QD swivels, buy the sling elsewhere and save $$, but if you do, consider that each QD is about $15.)
http://www.laruetactical.com/larue-tactical-padded-sling
I tried the Magpul MS4 sling, and found it cumbersome and a liability. The MS3 is easier to use than the QD's, but I still don't like stuff like that. You are fumbling with your rifle and have the potential to drop it when you should be paying attention to other tasks at hand, and not un-hooking your sling.
Again, the sling I linked you to is not advertised on the site as a VTAC sling, but it is. VTAC made it for LaRue (well, someone technically makes it for VTAC, I'm sure, but you get the idea).
Another point is that people don't know how to get the most out of their slings, often times, when first starting out. Here is a video that really helped me:
http://www.youtube.com/watch?v=YhojNCdksYw
FYI, all the stuff in that video he shows you...the product actually DOES. I remember how bummed I was when I got my brand new Magpul MS4, and I tried adjusting it and it wouldn't budge. The webbing was so stiff that I could stand on one end and pull on the other and it wouldn't move except at certain angles. It was infuriating. I even posted up on M4C about it (a place known for ripping idiots a new one), and figured I was in for the usual "Stop being a ninny" crap that people get for posting an "I find it difficult to...". No. Everyone started offering tips on break-in, complaining that they had the same problem, etc. So apparently it's not a personal issue.
Just something to take into account, not everything works as advertised, but I can vouch that the VTAC does.
This is my "Bipod"