Cnet: "Though we've kept you informed about the ongoing debate with the iPhone 4's antenna, we haven't said what that really means for users. You may see your bars drop when you hold the handset a certain way, but how does that affect the phone's performance?
In data speed and call quality tests (see attached video), we've seen significant changes when we cover the antenna gap on the handset's lower left side. Indeed, in one call quality test, the audio cut out completely when we covered the trouble spot. But to give those findings some context, we need compare the iPhone 4 with other AT&T devices.
In our experience from the hundreds of cell phones we've reviewed, attenuation on other handsets hasn't been as significant. But to be fair, we're going to test a few models again to see how Apple's device differs. Maybe it's worse, but maybe it's about the same."