We would like to emphasize that the iOS 4.0.1 update for the iPhone that Apple released does not fix the iPhone 4 “antenna issues” that some faced.
The update only mentions that it does the following: “Improves the formula to determine how many bars of signal strength to display.” So it only changes how the signal strength is displayed.
The following comparison by AnandTech shows how the signal strength is displayed as bars on the iPhone. First row is how iOS 4 displays the bars. Second row shows the strength in dB. Third row shows how the strength is displayed in iOS 4.0.1.
The following images were taken by Waleed Alzuhair which compares 2 iPhone 3GS phones, one with iOS 4.0.1 and the other with iOS 4. Taken at the same place we notice a difference in the number of bars.
Arabic version of this post on SaudiMac Arabic Edition.