Apparently, users are reporting that if they touch the outside metal perimeter of the new iPhone 4 they begin to lose signal:

iPhone 4 Loses Reception When You Hold It By The Antenna Band?

I'm willing to bet you that this is occurring because this time Apple didn't steal patents from other companies like Nokia. Their QA testing for their hardware is probably nothing compared to the huge labs Nokia has. I'm somewhat enjoying the fact that Apple doesn't know how to get the basics of phone hardware right. I mean isn't one of those basic things they teach people in electrical engineering.

I could only imagine the blood that would be spilled if a Nokia phone couldn't make a phone call successfully because you're holding the phone.

So I can faithfully say that I can indeed make phone calls on my N900 without losing reception.... and it's supposed to be an internet tablet device.