Let's start with guts. The Mini runs on an A5 chip—the same one that's in the iPad 2. The major upgrade to the A5 chip in this year's iPad (the A5X was sold as a graphical update at the time). That's a full three generations back now, with the A6X out now. This is almost certainly the same chip design that was die-shrunk in the upgraded iPad 2.
In all likelihood, the Mini has the same 512MB of RAM as the iPad 2 as well. A few reasons there. For one, it doesn't have retina-level numbers of pixels to push. But then remember that the die-shrunk A5 that it's using has never been paired with anything but 512MB of RAM.
You'll be hearing plenty more about the screen, but for now, it's 162.03 PPI, at 7.9 inches and 1024 x 768.