Just to address a few peoples' concerns about a genius bar replacement as a "refurb", "reconditioned", "remanufactured", etc.
None of those terms truly apply to what you're getting as an exchange. I know you just spent a lot of money on a new phone and don't want to get some inferior, used product to replace it.
A couple things to consider:
If you read the fine print of your warranty, it explicitly states that your exchange must be "equivalent-to-new". The fact that Apple may or may not use internal parts from other iPhones is irelevant; because you can't say that your product is equivalent to new unless it's the.. same as a new one! New glass, new steel frame, new buttons.. if they were just used on some other phone and then whiped off, they'd be "refurbished," not "new".
But none of this info REALLY matters because it really just boils down to your level of trust in Apple, as all the information you get from any Genius is heresay anyway. The actual process of how these parts are made is a secret that is not shared with many.
And the final argument I'll make is, if the phone you're getting has fewer symptoms than the one you're refusing to give up, where's the logic in that?