Below are the problem complaint by iPhone users

Apple said that's the reason behind widespread complaints from users that the latest model, iPhone 4, can show a sudden plunge in signal strength when they hold it in a way that covers a small black strip on one edge of the phone.

Apple responded by

The company said it will fix the formula to one recommended by AT&T Inc. through a free software update within a few weeks for the most recent iPhone models, 3G, 3GS and 4. However, the "wrong" formula goes back as far as the original iPhone, launched in 2007.

Full article at yahoo.com