That thin black bar seen on the bottom left corner of the iPhone 4 caused a number of issues for Apple in the early days of the smartphone launch.
The problem for some people appeared when holding the phone in the left hand. When the hand bridged the gap over that black bar, the signal dropped dramatically when out on the fringes of a network. Apple responded by giving away a free bumper or 3rd party case to all iPhone 4 owners.
Yesterday, Verizon launched the Verizon iPhone and one of the only changes noticed (other than the micro SIM slot not being there) was the change in the antenna. The regular iPhone has 3 black bars around the edges while the new Verizon iPhone 4 has 4 black bars. Verizon and Apple commented that this was because of the way CDMA works and that a new designed antenna was needed.
A number of bloggers such as SlashGear managed to run some tests yesterday and said that when holding the iPhone 4 the symptoms of the death grip seem to not be there any more. A few things to note though is that the location of the conference had a very good signal on Verizon, so until review units and actual units are sent out for sale we wont know for sure if Verizon users will have these changes. Also, we might find that in the next iPhone (iPhone 5) that the antenna for GSM models also changes to the new antenna.
Hope it will work out. Looking forward to it.