Apple has replied to the reception issue, stating in the following apple forum
http://discussions.apple.com/thread.jspa?threadID=fake2475309&thr=45&f=1
"We are aware of the reception issue, caused by bridging the two antennas.
Our manufacturing process is being reassessed and from now on will fix the issue, for those who have already purchased the iPhone 4, if you wish to fix the reception issue, please enable airplane mode."
http://discussions.apple.com/thread.jspa?threadID=fake2475309&thr=45&f=1
"We are aware of the reception issue, caused by bridging the two antennas.
Our manufacturing process is being reassessed and from now on will fix the issue, for those who have already purchased the iPhone 4, if you wish to fix the reception issue, please enable airplane mode."