The script will align (and lock) the vertex normals of the current selection to the normals of the selected faces. The effect is similar to Maya's weighted normals setting but the resulting normals will be "snapped" rather than just weighted.
This allows for smoother shading on low poly hard surface materials that use bevels. This will also result in cleaner normal map bakes with less gradients which in turn will cause less normal map compression artifacts.
More details in this blog post:
The script can be downloaded for free from Gumroad: