What makes Core Temp unique is the way it works. It is capable of displaying a temperature of each individual core of every processor in your system!
You can see temperature fluctuations in real time with varying workloads. Core Temp is also motherboard agnostic.
All major processor manufacturers have implemented a "DTS" (Digital Thermal Sensor) in their products. The DTS provides more accurate and higher resolution temperature readings than conventional onboard thermal sensors. (How does it work?).
This feature is supported by all recent x86 processors. Processors by Intel, AMD and VIA are supported. A complete list of supported processors is available.