Supposed to be good if you're running SMP (multi-processor) with Win2k...something about Win2k not being able to execute the HLT command on both processors. Not sure if that's true or not.
Also, it's supposed to cool the chip better than Win2k's built in routines. Don't know about that either, since I don't have an accurate way of measuring my CPU temp at idle. Some say yes, some say no. I liked the numerical display of CPU usage in the taskbar. In the interests of system resources, I've uninstalled it. I doubt it uses much resources anyways.