Let’s start with the weight:

Here’s a breakdown of weights:

iPad 1 – 712.60g
iPad 2 – 600.60g

iPad 2 – 112g lighter

ipad 1 front half(LCD & Glass assembly) – 347.90g
ipad 1 back half – 364.70g

ipad 2 front half(LCD & Glass) – 263.20g
ipad 2 back half – 337.40g

Where’d they save the most weight? I’d say with eliminating the frame that the glass sits on, using thinner LCD and thinner glass, they saved 84.7g. That makes up for 75% of the weight reduction.