Well, this is a first for me. I was cleaning the glass on my new iPad this evening under a bright LED spot and I noticed a streak/smudge, so I attempted wipe it away with a damp cloth, but it remained. On closer inspection, it became clear the finger swipe was on the bottom of the glass! Since it's not visible when the iPad's in use, nor under ordinary incandescent or fluorescent light, Apple may not want to do anything about it.
I have an appointment with the Genius Bar tomorrow to see if they'll swap it out for me.