Like always, Matt Richardson is all over it!
Check out his full post on Makezine. Here are some specifics:
The processor gets a bump up to 1GHz, compared to the original’s 720MHz.
RAM is doubled to 512MB.
The BeagleBone Black can be connected directly to a monitor through the on-board MicroHDMI port.
They’ve added 2GB of on-board flash memory, which will be preloaded with the Ångström distribution of Linux. This is in addition to the MicroSD slot, which you can still boot from, if you wish.
The software gets a big upgrade, too. The provided Ångström disk image is now on Linux Kernel 3.8. They’ve also made many improvements to BoneScript, their node.js library for physical computing on embedded Linux. This new disk image is will be available for the original BeagleBone as well.
Perhaps best of all, BeagleBoard.org has slashed the price down to a mere $45, pitting it much more competitively against the very popular Raspberry Pi, which currently sold for $35.
Also, if you're new to BealeBone, Matt's book, Getting Started with BeagleBone, is now available for early release in ebook form.