Update: So the iFixit disassembly continues, and some interesting tidbits have emerged. The battery is pretty huge -- a 3.75V, 24.8 watt-hour job, weighing in at 148 grams. There are some significant differences between the retail unit and what we saw at the FCC, including the A4 processor, which looks to be manufactured by Samsung.
Update 2: Talk about some wild findings. The iFixit crew has discovered that the iPad's battery has 5.5x the capacity of the battery in the iPhone, with two batteries wired in parallel, for a total of 24.8 Watt-hours. On average, the unit sips just 2.5 Watts (one-fifth the power of a compact fluorescent bulb), and the rear case is machined from a single billet of aluminum. We're told that the "empty void in the upper right corner is where the cellular communications board would go in the 3G iPad," and "the A4 is a Package-on-Package (PoP), with at least three layers of circuitry layered on top of each other." Care for more? Head past the break for the bullet points.