One bit of remaining scepticism for me is the claim of using the casing edge as antennas to improve reception. Although I'm willing to be proven wrong, I think this claim is bogus, just as it was for the previous generation phone where they claimed the ring around the headphone jack, the camera, and the front chrome bezel were used for antennas. (When clearly they were not - they're all loops, and they're not connected to anything...)
First of all, the lengths of the metal are not even close to the correct length for the frequencies they're trying to transmit - they're actually too long for 2100Mhz for example, but the biggest problem of all is the fact that you are touching the supposed antenna when you hold the device. Any RF engineer can tell you that if you make electrical contact with an antenna by touching it, it seriously detunes it to the point where any improvement that you might have had from the antenna being external will be lost and then some.
Even if they coated it with a thin non conductive layer, the close proximity of your hand would still have a serious effect on the tuning and performance of the antenna, as even conventional internal antennas in phones which are held at least a few mm away from your hand suffer from significant performance loss from the proximity of your hand, and this whole issue of hand proximity is one of the biggest challenges in antenna design in mobile phones.
So until proven wrong I call BS on Apple's claim of improved reception by using the frame as antennas. If there is an actual improvement in reception then it's more likely to be the glass back (which is far more transparent to 900-2100Mhz radio signals than ABS plastic is) or an improvement in the internal antenna designs, or different radio chipsets, or a combination of the above.