It is not only iPhone 4 with antenna problem. My 3GS does exactly the some. When I put it into my dock I have full reception, but when I take it into my hand it is getting almost no signal at all. It applies to poor reception locations only. When I am in place where is very good signal then this problem is hard to notice because I get one or 2 bars less (3 out of 5 is still good signal). When I am in low reception area I still have full 3G as long as I do not grab the phone, it needs to stay plugged into a dock and then works without any problem. Tested and confirmed on 2 phones.