ITreviewed posted a review on the Western Digital Caviar Green 2TB

As hard drive capacities increase, the power required to run those drives increases as well. WD's WD20EADS makes it possible for energy-conscious users to build a system with massive storage capacities and the right balance of system performance, ensured reliability, and energy conservation. The drive is also environmentally friendly due to relatively lower power consumption, and it runs cool and quiet operation. What more can you ask for? Well, speed is a tad disappointing - the WD20EADS lags behind smaller-capacity drives such as WD's RE3 Enterprise 500GB and VelociRaptor. This is due largely to the fact that the drive's rotaional speed is 5400rpm, which results in a latency of 5.5ms rather than the 4.2ms you typically get on a 7200rpm drive. Unless you're a speed junkie, you should be more that satisfied with its 11p per gigabyte up-front cost and green credentials. Before you take the plunge however, it's worth noting that Seagate is hot on WD's heels. The company's 7200.12 (2TB) drive should be out soon, so then it will be a battle between who has better transfer speeds (and a better firmware, apparently). Since the 7200.12 is supposed to be much faster than the company's 7200.11, Seagate will probably take the speed crown.

Western Digital Caviar Green 2TB Review