I've got an Oly K4B (20" A2 Duty/Match) that I bought just after the AWB went away. I've also got 2 other AR's built on Stag lowers, one with an RRA upper, Oly B/BC/CH, Oly FIRSH railed handguards and Oly fiberite telestock, and the other built from a J&T CAR kit.
The Oly is the equal of the others and is the most accurate. A couple of thousand rounds so far without a single hiccup. All the Oly products I own are excellent. My contacts I've had with Oly's reps have been excellent as well.
Oly also makes all the parts in the rifles they build, including the upper and lower receivers and the barrels. I don't believe any other company producing AR's can still say that.