Some users are reporting an issue where the newly shipping Apple iPhone Bluetooth headset generates a "stuttering" sound -- audio going in and out, perhaps caused by interference. Users noting the issue report that it only occurs when using the Apple Bluetooth headset, not the built-in iPhone earpiece or other headsets.
In some cases, the issue is more pronounced the further iPhone is away from the headset. Even something as subtle as keeping the iPhone in left pocket and headset in right ear (instead of both on the same side) may generate the problem.
If you're experiencing a similar issue, please let us know.