I want to buy an IPhone, and I realize that the only cellular service is through AT&T/Cingular; but are there any advantages to purchasing it directly through Apple and then going to AT&T to activate?

What I'm wondering about is service/warranty/repair issues. Would Apple more likely/easily service your phone if you bought it directly through them. Similarly, would you not be able to to take advantage of certain specials/deals offered by AT&T if you didn't directly buy it through them when activating?