I'm not sure why some of you can't tell much of a difference. Maybe it's time to get a "powers of perception" checkup
I've had every iPad except the 4 and have a 2 and 3 and Air in the house right now. The difference in weight between the 2 and the air is quite significant, in fact I would just stop short of saying it's dramatic.
I never get tired of holding the Air in one hand or feel like it's digging into my leg when I have it propped up. It feels like a whole other class of device to me.