Let me start by saying that the Kindle 2 is a nice upgrade over the original Kindle, but we're not talking a jump from, say, black-and-white television to color, so early adopters who own the original Kindle shouldn't feel too dejected.

Yes, the Kindle 2 is thinner--it measures a svelte 0.36 inches at its thickest point--and weighs in at 10.2 ounces. It also has 25 percent improved battery life and is about 20 percent faster, thanks to an upgraded processor. And it's got 16 shades of gray instead of 4, so the text pops a little more. But this is an evolution, not a revolution.
Source:http://reviews.cnet.com