This could be interesting.
Per The Unofficial Apple Weblog, Apple surprised its audience by announcing the Fusion Drive, a combination of SSD and HDD technologies. Fusion Drive is part of the new, just-announced iMacs, and is supported by OS X 10.8 (Mountain Lion). In concept, it’s similar to auto-tiering that is used in enterprise environments.
In practice, Apple is offering a 128 GB SDD with a 1 TB or 3 TB HDD drive that are combined with smart software. The OS will monitor which apps you use the most and runs them from the SDD. Apple claims that, when the system is idle, it uses 50 percent less power than a standard hard drive.
Stay tuned for additional details as they become available.