Apple has released iOS 4.1 SDK and beta for the iPhones which are running over iOS 4.0. Specifically, the iOS 4.1 includes iPhone 4 signal bars fix which was explained by Apple previously when company said that the formula used to calculate bars of signal strength on iPhone 4 is inaccurate which needs a fix.
Apparently it seems that iOS 4.1 focus is to provide a fix to signal bars display which means a better makeover to bars.
So, we will update the post if we find new features of iOS 4.1 as a fix for iPhone 4 reception and call dropping issue.
You may download iOS 4.1 through iPhone Dev center by clicking on integrated link.