You know, I've been reading all this stuff, and was a bit worried while I waited for my iPhone4 to arrive. Since then, I have traveled to 4 countries on business, and have been a long distance train through rural areas. I have tried everywhere to use the death grip to drop the signal to 0, but I can't. I can't get it to drop a call, and I can't get it to lose signal - I can get it to 1 bar but I can still surf on 3G with that, and the call quality has been fine. I've used overseas carriers' SIM's too...And I'm left handed, and have no case.
At the end of all this, I've simply decided that for me, this phone is the best I've had, and I have no problem with it in any way. I'm just glad I won't have to read all this stuff and worry any more. Sorry if you have problems, but as everyone says, take it back. Being a long time Mac user I have no problem using equipment that is not the most common anyway.