It has the same 77.5 watt-hour battery as last year's MacBook Pros, faster RAM (matches the last iMacs), an antenna bump from three to four for the wireless card, and slight quality control issues that might cause overheating problems down the line. iFixit is unsure.
The other interesting bit is that Thunderbolt can only handle chaining six devices, whereas FireWire can go up to 63 and USB up to 127. If you're only doing displays and storage devices, that seems fine, relegating keyboards and mice and other, less data-intensive peripherals to USB. [iFixit]