I agree with you...I think the 3g launch could potentially be larger. You have tons of folks who have been desperately waiting for the 3g release. You also have the folks who bought wi-fi units and will be waiting in line to exchange their purchase for a 3g unit.
I was thinking about going and getting one in addition to the one I have being shipped on Friday - I would then have one to play with on my trip and could sell the other one to a friend or online. I'm not an online seller, but doing it once can't hurt - and I'd probably just set the reserve to cover my costs plus my time (I'm not expensive either LOL).
They should consider a separate line for those returning items, as that could severely clog the line. If they could do exchanges for people while they are waiting, that could help speed things up.