With my iPhone 3G jailbroken with iOS 4.0, lots of other users have been experienced cell phone reception trouble. I tried it myself and covered the left side and saw my signal bars drop by 4. I've read around the internet and its rumoured that 4.01 was supposed to drop today to fix the antenna issues. I'd assume before Friday, there's going to be a fix out there. I, myself, didn't have too much trouble with getting a signal.