Among many tech blogs and news sites there have been consistent complaints about the inconsistency of many iPhone 3G’s.  The inconsistency arrives when browsing the web or taking calls.  Many people including myself have experienced dropped calls or poor quality.  Also when in an area with 3G the phone regularly changes to EDGE for its connection.  Many reports say this is a result of an Infineon chipset which is "immature".  Hopefully this trouble is remedied thru software/firmware updates.  There have been reports of this being a problem with the chip itself or possibly the software.  Either way you can bet Apple will have an update quickly.