The iPad is basically an iPhone with a 6 bit IPS screen and a bigger battery!
http://www.chipworks.com/Apple-iPAD-Teardown.aspx
From the article:
"Apple has relied on tried and true technology for the first generation of this device. In some cases, technically speaking, Apple has even gone backwards from what we saw in the latest generation iPhone that we have torn down.
Case in point, Apple is not using the do-all touchscreen controller from Texas Instruments that it used in the iPhone 3G, but has instead gone back to the three chip solution seen in the iPhone 2G. Of course, the same space limitations aren't there in a large device, and so we would speculate that the three chip solution had a lower overall cost. You can see from the image that, relatively speaking, the iPad is basically a giant battery with a tiny board attached to it (outlined in red), with some space left over for a future 3G mobile communications board."