It's hardly a new problem, or unique to the iPhone.
Extract from the manual for my phone:
Your phone has a built-in antenna. As with any other radio-transmitting device, do not touch the antenna unnecessarily when the phone is switched on. Contact with the antenna affects call quality and may cause the phone to operate at higher power levels than otherwise needed.
It's a Nokia 3310, purchased at least 10 years ago.
As Apple say (in effect)
here- if holding the phone in a particular way affects the call quality, don't hold it that way.
Edited by billford (Fri 25-Jun-10 09:53:52)