My understanding is that there's one difference between this type of attenuation and the one that plagues the iPhone 4: one can apparently reproduce the reception attunation on the iPhone 4 just by touching the place where the two antennas meet on the lower left case.
With the other phones, the problem is caused by the proximity of the hand shielding the antenna, whereas with the iPhone 4 it is caused by direct contact with the antenna itself, and thus is a bigger problem. It also explains why adding a relatively thin Bumper case to the iPhone 4 pretty much eradicates the problem. As would--I presume--coating the iPhone 4's antenna with a clear insulating layer (clear so that the phone's aesthetics are preserved).
The iPhone 4 comes out here next Friday (the 30th), so I'll play with one to see for myself how bad this problem really is.
