I just got my AAC M4 2000 on Friday. I shot it on two of my AR's over the weekend, an Armalite M15A4(T) and a S&W M&P15 T.
POI with the S&W was pretty much dead on with the red dots zero, with the Armalite, it was about 2" low, and 2" to the left.
I also got a AAC Eco-9 for my Glock 17, and it was dead on. The Eco-9 can supposedly be adjusted for POI, but it wasnt necessary with mine.
300 rounds of 9mm, and 100 rounds of 5.56, no ear plugs, and I can still hear. No more ringing or crickets than usual either!