It comes in 2TB and 3TB capacities and features 2 additional USB 2.0 ports. Naturally no USB 3.0 ports since Apple does not support USB 3.0 (at the moment), but it would be better if they had included Thunderbolt in anticipation of future Thunderbolt-supported devices. It connects to your Mac computer via USB 2.0 or one of the two Firewire 800 ports.
The hard drive is reformatted in HFS+ to work with a Mac out of the box. It has also apparently been designed to fit perfectly on the base of the iMac or an Apple LCD. It also features a storage gauge in the form of four little LED lights, with each representing about 25% of its capacity.
It looks like a pretty nifty device for Mac computers although it will cost more than your regular external hard drives at about $195 for the 2TB version and $295 for the 3TB version. If you could do with the additional ports and love the fact that it was created specifically for Mac computers, they will be available from Apple retail stores.