I was recently reading where the author was actually claiming that the carry handle is a dated feature of the AR15/M16 and is a hazard to safety because when the weapon is carried by the handle it is pointing either forward or backward. In a fuzzy sort of way, I could see the logic of that opinion but I completely disagree with it. I don't many people who are trained to carry an AR15/M16 by the carry handle anyhow. One of my favorite field expedient methods of carrying it while moving quickle is to put my thumb through the carry handle and wrap the rest of my fingers around the front of the magazine well. This method is quick, easy, provides for a firm grip on the weapon, and the weapon is generally pointed in a safe direction.
I think that the ruggedness of a carry handle is an absolute must on one's primary AR15. In either A1 or A2 form, it goes right to the heart of the KISS principle. No detachable handles to keep track of, lose, or worry about losing their zero. I do have a couple of flat tops that will eventually be built into dedicated scoped target/varmint rifles, but the good ol' Colt R6550 with the A2 carry handle is what I would fall back on when the chips come down.