Not too long after making us all salivate with the announcement of a 1TB drive, Seagate will be releasing a 15k RPM 2.5-inch hard drive under their Savvio line of drives. The enterprise class 2.5-inch disk drive only stores 36GB even with perpendicular recording technology, while the 3.5-inch version stores 73GB. For the first time in a while, the smaller 2.5-inch drive actually has the upper hand for many reasons - decreased power consumption, amazing seek times (2.9ms) and increased reliability. Datacenters have their eye on drives like these for lower power requirements.
Unfortunately, you won't be sticking one of these in your MacBook Pro or consumer-grade computer any time soon. The Seagate Savvio drive utilizes SAS for its connection. SAS is significantly different from SATA, which is used in most modern consumer computers. Wikipedia sums up the difference between SAS and SATA quite well:
SATA is primarily used for non-critical applications like home PC use while SAS, due to its robustness, can be used for critical server applications. It is designed for the corporate and enterprise market as a replacement for parallel SCSI, allowing for much higher speed data transfers than previously available.