I dropped by the Apple store to do a little experiment for my own benefit and to check out the iPhone 4. First:
It's beautiful. The screen looks awesome, the interface is snappy, and the camera rocks, even in the fluorescent lighting of the Apple store. Protip: it's really fun to scroll through the camera memory to see all the people who took pictures of themselves.
What I did:
I walked around to the iPhone displays (12 of them) and held each phone deliberately trying to cause the problem. I held the phone in my left hand with the seam directly in my palm. I held each phone there for about a minute, sometimes less if the issue arose faster than that. I did not make any calls, and I relied only on the meter to tell me if the reception went away.
Results:
The signal dropped to one bar on all 12 of the phones. The signal never dropped to "No Signal". Because I did not attempt to make any phone calls, I do not know if this caused the call quality to be bad or diminished at all.
I also asked some people who were beside me to hold the phone in the same way. Sure enough, they saw the bars go away as well.
Conclusions:
There definitely is an issue. Since I only tested phones from one Apple store, it could have just been that this Apple store got a bad batch. An apple employee mentioned that the problem may have been related to a certain build week. Generally, retail employees are full of crap though.
I wouldn't advise you to run back to the store and demand your money back. It is possible that a software update on Monday will fix these woes. However, it is also possible that this is a hardware problem, so if you haven't already ordered one, I'd advise you to hold off, or order one with caution.
Obviously, this wasn't a scientific test. But for me, it was enough evidence for me to hold off on ordering an iPhone 4.
iPad2 16 GB
iPhone 5 32 GB
iPad2 16 GB
iPhone 5 32 GB