Don't know about replacing it. It always seems to me it's a tradeoff between accuracy and reliablility. M-16 is built tight, so therefore more accurate, but it doesn't like dirt. I own an SKS, and it's a loose rattle-trap, not very accurate, but the thing doesn't jam. My own meager experience with the M-16 A1 was firing it only every 2 years in the AF. Good reliability when it was clean. But I also remember a trip to Ft. Drum using MILES gear with it, firing blanks. The blanks burned very dirty, and everyone's rifle jammed up after a dozen rounds or so. Didn't like that. In close quarters like Bagdhad, I'd rather have something that keeps going when it's dirty.
Now the Marines are going to jump on me because I didn't clean my rifle after every other breath. :) Flame suit on, diving into the ditch, preparing for incoming.....
I also doubt the Iraqis we will train will be fastidious in cleaning M-16 rifles so it makes sense that they will be issued AK-47s.