If you have had problems with the 3G part of your new iPhone be sure to pick up the new 2.0.2 firmware. Apple has confirmed that it fixes some glitches related to the communication with 3G networks.
Apple: iPhone 2.0.2 update targets 3G issues [appleinsider.com]



It didn’t fix shit. Shit got worse. Thanks apple.
[...] Apple’s update was released in an attempt to fix some of the issues relating to 3G on the iPhone well over a week ago, there have since been version updates released for various [...]