I hear and understand a lot of the grief given the M16/M4, and I'll just add this -

My issued M4, which I maintained reasonably (as opposed to spotlessly)downrange, never failed me in over 300 rounds of service use. Never had a jam on a range either.

I can't really say I saw any major issues with any of my soldier's M16's/M4's downrange, as long as they cleaned them regularly (wipe down daily, detailed 1x/week)

Stopping power is another discussion, but fortunately there aren't a lot of big burly Iraqis.