I went with the Magpul MS3 Sling in the Coyote Color. I had a gift certificate at a LGS. It was $59 + tax. It is a two point or one point sling. Haven't used it yet, but will once I get my MP15. Currently on my 15-22. I did have to get a QD Mount from Magpul that went on the front hand guard. My 15-22 has the built in QD in the lower on the Magpul MOE version.
+1 on the MS3 sling. I've got several that I use for single point carry, but it can also do a two point carry due to the flexibility of the design.
I've got the OR model as well - it's a solid platform and don't think you could go too far wrong, but there is additional cost for sights, be they iron, optical, or both.