nik Color Efex Pro filters are enhancement filters that work within Photoshop, allowing you a multitude of easily attained effects. Depending on which edition you get, there are up to 75 filters with which numerous effects and enhancements can easily be used on any digital image.
According to the nik literature, it uses a “True Light color processing system” to consider the existing color and light information in an image to automatically provide optimal enhancements. In this way the effect is adapted according to the picture info such as detail, colour and contrast range. They also claim that by identifying the unique qualities of the image that the filter is processing, each filter is able to achieve consistency across a range of images.
However it may work, let me tell you - it does work. Colour me impressed.

