hmmm... looks like they are backing out the 2.1 OS fix that "Improved accuracy of the 3G signal strength display". That always seemed fishy to me.

http://gizmodo.com/5048905/iphone-21-update-available-now

Especially entertaining is the update note at the bottom:

The "3G signal strength display" fix certainly seems to have done something for my iPhone 3G: it's sitting here in the same place on my desk, and has gone from two bars of 3G signal with the 2.0.2 software to a whopping five bars in version 2.1.