I just got a replacement iPhone 4 for the iLemon that I've been blogging about here lately and, so far anyway, the Bluetooth problem seems to have disappeared.
I haven't had a chance to test it exhaustively yet (it's only been a few hours), but I was intrigued by this blog post at iFixIt about how Apple may be applying a non-conductive coating to the metal frame on the second-batch of iPhone 4s to help mitigate the antenna issue.
The interesting part is that iFixIt details how to decode the iPhone's serial number:
aabccdddeefaa = Factory and Machine ID
b = Year
cc = Production Week
ddd = Unique Identifier
ee = Color (A4=black)
f = size (S=16GB, T=32GB)
The serial number on the unit tells you the manufacture date; our original phone was manufactured in mid-June (week 25). The replacement unit we got was made in early-July (week 27), apparently too soon for a manufacturing change.The serial number also identifies which factory it was made in. (We don’t have a mapping of numbers to physical factories, but we can tell if two phones came from the same plant.)
My serial numbers:85025xxxA4T (original 32GB iPhone 4- June 24)
86027xxxA4T (replacement - July 15)
My replacement iPhone 4 is a week 27 unit, fabbed a scant two-weeks into the production process and too soon for a manufacturing change.
If you've had your i4 replaced, post your serial number (minus the unique bit) in the TalkBack below.