Apple's iOS 4.1 issued to developers, reception tweaks ensue
After the update, a difference in signal bars visualization is observed, when comparing an iPhone 4 with and without iOS 4.1. The first three bars are taller now, and reception seems to be more aligned with the reality of the AT&T signal - at places where iOS 4 shows five bars, an updated phone shows only three.
If visual delusion were the issue, it probably wouldn't have muddied the Apple juice for weeks on end. Now all that's left is to wait on that conference tomorrow, with baited breath.
Apple iPhone 4 Specifications | Review