This example 480x360 is from a 1600x1200 render and is in PSD 7 file format.

The Layers contain post process, refraction, reflection, shadow, specular, diffuse and background. Channels are alpha, depth, view normal, shadow, normal x, normal y, normal z.

Download and see for yourself the time saving that can be achieved with this type of file.

You may have to R-click and save target as.