(Updated with higher res image. Click to enlarge)
A. You can see here that the mounts for the logic board are very different, which means the logic board shape will be different allowing for . . . .
B. More battery. The width of where the logic board sits on the iPad 2 appears much larger than that of the iPad 3. We have long heard that the iPad 3 was going to provide longer battery life, and this back housing seems to support that. [Ed: Actually, this could be to compensate for the additional power draw of the screen and possibly a faster processor]
C. The camera is different. It is hard to make a judgment just by looking at the casing, but what we can expect is a different camera on the iPad 3 than what we had on the 2.
D. LCD will be different than what we have had before. Whether or not it will be the super screen we have seen reported will have to wait. But the different mounting does mean that the LCD has been redesigned at the very least.
The report said the iPad 3 case was not noticeably thicker than the iPad 2, countering previous rumors that the new iPad would be thicker.
It is hard to vouch for the authenticity of the case above, but the changes mentioned do seem to mesh with what’s floated around.