The 5.56 mm round comes off rather well. I'm not so sure, for all the reasons listed in the article. I'm not a huge fan of the 5.56.
One comment that piqued my interest was
Much experimentation has taken place to develop the "perfect bullet" and at present it appears to be something between 6mm and 7mm.
Word on the street from Huggy Bear is that USSOCOM is fielding new upper receivers for the M4 that chamber a 6.68 mm round. Would love to hear the feedback on those.
One important point on round development is that, in this blogger's humble opinion, you cannot discuss the "goodness" of various calibers in combat without acknowledging the revolution in optics that the military provides its servicemen. Most sights now are "aiming dot" type optics, in which the aiming point is the focus of a parabolic lens. Used to be, soldiers had to line up the iron sights of the weapon, and had to have the correct "sight picture" in order to actually hit the target. In fact, "sight picture" was one of the three fundamentals of shooting (the other two being breath control and trigger squeeze). So, the soldier's eye, the rear sight aperture, and the front sight post all had to be in line for the soldier to hit the target. And the soldier had to do it the exact same way every time, with his head in the exact same position in relation to the sights of the weapon. Now, when the troop puts the aiming dot on the target, that is where the round will strike (given that he doesn't hork up breathing or trigger squeeze) no matter what the relief of his eye to the sight is. This makes potentially problematic rounds, like the 5.56 mm, extremely more effective, since round placement on the target (nice word for "bad guy") is going to be consistently better.