Went to the AT&T store and ported my number back to the 3G iphone. Back to no dropped calls and no proximity sensor issue. Withdrawal symptoms, none so far!
Next step - return the iphone at the apple store.
And those of you who are upset about this thread, I wonder what your motive is. Why do you so vehemently defend, a new revision of a product that is flawed. The answer to that could be that you own apple stock and you can't stand to see the price of the stock go down.