Apple fanbois will tell you this is no big deal. You can still complete calls rather easily by using the speakerphone keeping the phone on your desk, If that doesn't work, you can put on winter mittens or last resort, you could cover your hand in Vaseline or high viscosity oil to minimize interference.
The up side to all this, not only will these solutions reduce call drops but it will send an arrogant and eloquent message to everyone around you that you are hip and cool with the new iPhone 4!
I speculated that this would happen in another thread regarding the iPhone 4 and its' construction. Sure enough it has happened. An accidental 1 foot drop and the BACK of the iPhone 4 shattered. Nothing like having a glass phone! LOL!!!