Apple apparently moved the iPad 2's microphone to the top center of the device, and that's causing problems in performance across the Wi-Fi and 3G models, says iLounge. The 3G model's mic is set in a different material than the Wi-Fi version (because of the extra antenna), and that means that the Wi-Fi version sounds "markedly cleaner" than the other versions, with the CDMA model sounding the most "slightly muffled and echo-prone." The problem is reportedly exacerbated when the mic is facing away from its target, like when you're using the iPad for FaceTime.
I doubt this is a dealbreaker for most users, but it is probably something we'll see fixed in the next version of the iPad -- it's interesting that this either never
