The test was conducted by Bluetest, a small company that sells test chambers for wireless devices with small antennas, and the results were compared to a Sony Ericsson P1 and a Nokia N73. The bottom line of the tests were that the iPhone was on-par with the other phones.
Testing was only done with one iPhone so it does not eliminate the possibility of a manufacturing defect, however the author notes that before the test the iPhone had been registering lower 3G bars than the Nokia model and would be more apt to switch to the EDGE network; symptoms common amongst users with the connectivity issue.
BusinessWeek (and later a memo from Steve Jobs) has previously reported that the issue was to be fixed via a software update. Since then, iPhone Software 2.0.2 has been released claiming to fix the problem, though users have still reported the issue.