Guys i don't know if this is helpful or not but i thought i would post it anyway.
So in total i have three iphones (older models i have not got around to selling yet), I have the iphone 4, 3GS and 3G. So my iphone 4 obviously has 4.0 on it out of the box and of course features the antenna issues but here is my belief that it is related to the baseband. My 3GS was running 3.1.2 with baseband 04.26.08 however i updated it to 4.0 and baseband 05.13.04 i encountered signal issues so i downgraded the firmware back, so it now has 3.1.2 with baseband 05.13.04 and yet i still have the same signal issues. My 3G remains untouched also running 3.1.2 but with baseband 04.26.08 and it has no signal issues.
These are my reasons for believing that the problems the iphone 4's are having are down to the baseband
Yes i am aware that the iphone 4 has a new baseband 01.59.00 but for all we know it could just be the same but re-numbered
Let me know what you guys think, Its just my theory on it
Edit Update:
Guys something odd here, Im on pay as you go with an unlocked iphone 4 direct from apple, I have my microsim card from O2 and the death grip is a real issue, I got a 3 simcard and cut it down to microsim size put it in my iphone and i CAN NOT make the signal go down at all with the death grip
I just posted a thread on my baseband errors on iPhone 4: It seems like every time i go and sync my phone, i get the box to send error reports to Apple. I click "more info" and it has several baseband error logs. I clear them out each time and the next time I sync there's even more?? Maybe this could be related??