Apple have released the official reply/statement to the complaints they received against the iPhone 4. They start off by complementing the iPhone 4 stating that its their most successful product ever and that reviewers and customers are extremely happy with the device.
They say that most phones experience 1 bar of signal drop when held tightly. But many users report that there is a 4-5 bars of drop in reception on the iPhone 4 and say that it has got to do with fault of the internal antenna.
On the other hand Apple claim that they have received mails suggesting iPhone 4 has better reception than the iPhone 3GS.
They go on to report the full report after they investigated the problem. You can read about it in their official press statement here.
They even offer customers a full refund if they return their undamaged iPhone 4’s within 30 days of purchase.