I don't have the robotic issue either, but I seem to have the same problem as others and it manifests itself when I am on a phone conference in which other members are on the other end with several talking around a speaker phone. Invariably there will be a couple around the mic on the other end that are further away, or talk low. Now, usually (with various Blackberries I used for the last 5 years in this use case) you just can't hear those people well, or you would have to increase the volume of the phone to hear them. But you could hear that they were talking. It was not broken up, not choppy.
Now, with the iPhone 5, lower volume talkers get chopped up. You hear them for a second or so, then don't for a second or so, and it repeats, and when you don't hear them you hear silence.
If I ask others to get closer to the mic and speak up, it helps, but for the most part since switching to the iPhone 5 I have become a nuisance on the phone when conferencing with others, and I have missed a lot of the conversations I am in.
So, I do think it is faulty white-noise detection as others have suggested, and I think it is insane that this didn't get caught in QA.