FWIW. I believe OP.
I took back my old iPhone 4 because of overheating issues; it would be sitting on my desk in an air conditioned room and I would get the "You need to let iPhone cool off before using it". Also my old phone had the death grip issues and the magic hang up spot.
Got a refurb, week 32 (starts with 5K) and I can confirm that the metal band feels...different. Hard to describe, but it feels "rougher"? Like its not smooth, polished steel. On this phone, I am unable whatsoever to cause the death grip issues. The dropped calls have stopped and I have a "cooler" screen. My old phone had a yellowish screen.
Believe him or not, just dont flame him. Sorry, Im not going to "scratch" my phone to prove it to you. Nor am I going to buy a digital thingamajigameter to measure Ohm resistance.
Refurbs do go through a far more intensive QC inspection process than FOB phones do.
It could be that they added capacity to the local towers in the area but I'm going to give Cupertino the benefit of the doubt and say that something was fixed. (Reception is still kind of junky on the 3gS)
And I also had 5K (week 34) (it was replaced for a faulty home button), which I was using for a month! And no way the bezel is different on 5K models: it was identical to my previous 86 (week 34), 85 (week 29), and my current 88 (week 32). And I know what I'm talking about: I've been using the test field mode on my last two phones, it's always there instead of the regular bars. The 5K had the same signal strength as my current 88 does in all different areas, and they're both affected the same way by the death grip (usually, 2 bar-drop, 20-30 db).
It depends on the area you're at, so you guys should stop dreaming about the silent fix. Really, it's getting redonkeylous