Apple spokeswoman Jennifer Bowcock said on Tuesday, "The software update improves communication with 3G networks."
iPhone customers have complained about dropped calls and other connection issues with the 3G iPhone. Apparently these drops occur when 3G service becomes unavailable and the iPhone switches to Edge during a call.
NOTE***: If you plan to jailbreak or unlock your 3G iPhone please wait until PwnageTool is updated for 2.0.2. Do not upgrade via iTunes.