In addition to the extra real estate, this model offers an iSight camera, mic and speakers, plus a powered USB 2.0 hub (3 ports) and MagSafe connector to charge your laptop. The display includes ambient light sensor, which adjusts the display's brightness in response to the light in a room.
Apple's also keen to describe the display's environmental friendliness, noting that it uses mercury-free LED technology, arsenic-free glass and recyclable materials. Additionally, the display meets Energy Star 5.0 requirements and achieves EPEAT Gold status.
It sure sounds nice, and it will be available in September for US$999. Note that it requires a Mac with a Mini DisplayPort.