Dear Mr Job,
You know, and I know, that it is not good enough telling people ‘not to hold the iPhone4 a particular way‘.
The problem qualifies as a serious design flaw, and I am sure you found it out during your usual testing before launching it. I do not think you found that out only after yesterday’s launch, but perhaps you failed to notice the seriousness of the problem until yesterday.
Regardless, my electronic engineering degree tells me that if you put a small distance between one’s hand and the antenna, the situation can be improved dramatically. And guest what? You already have such a device ready. I am not sure what you call it, but people appears to call it the bumper sleeve.
If using the bumper sleeve will improve the reception, I hope you will do the right thing by your customer by giving them one free. It will cost you pittance, but buy you a lot of good will. Furthermore, you are actually rewarding loyal customers of Apple who queue up for iPhone, something most people, like me, would not bother to.