Now, I'm not one to blog about the newest tech news or anything, but Apple has released iOS 4.0.1 which as they say, "improves the formula used to calculate the appropriate bars for signal strength". Available in iTunes and here. I've always had a cheap plastic case on mine, so I never noticed any reception loss greatly. Although if I do hold it in my left hand for an extended period, I saw 5 bars go to 1 bar.
Firmware 4.0.1 is jailbreakable with the 3G so far, so 3GS and 4 users are out of luck. If the only entry in the change log is the "improved formula", I don't see the need to update personally. Sure, it may say I have 1 bar, but hey, as long as it works.