I have noticed this and it is pretty irritating, it is that when ever i decide to floor the car(VERY often) the A/C feels like its cutting out and i get this musty stale smell from the fan vents (notcool), then after it kicks back on and all is good, until i stop and floor it, then it happens again, I WILL have this addressed at the 7,500 K maintenance, along with the Reflash. The A/C does have a problem keeping up in hot climates. Also I have never noticed a difference in MPG with the air conditioning on or off in any of the cars I have driven. Heres my MPG report (mostly city/aggressive driving)
Mobil-15
Shell-17
Chevron-16-17
Valero-15