Combining the falloff sop with a few groups is a great way to control attributes by distance without having to jump into VEX and VOPs. A lot of sop nodes output groups along with the operations they do so I figure you might as well use them when you have the chance. Here are a few examples of the falloff sop in action.
I had to build a custom fracture setup for a job based on getting a specific look. I was using The Voronoi Fracture sop and I wanted a controllable distance from edge where the inside and outside meet. The Voronoi Fracture sop outputs an inside and outside group and with a bit of group compositing I could find the edge and use the falloff sop from their to create my distance from edge attribute.
Another use is to create a distance attribute from the border of an object with unshared edges. I used the falloff node in this way as a quick base attribute to create a lake with depth from a flat grid.
You could flip that around and create a mountain peck as well by adding to @P.y instead of subtracting. Which could be used as a way to hand sculpt base shapes for driving the terrain tools. So far I have been using the Surface Distance mode as the distance metric in first two examples but if we switch the distance metric to edge we get a result that looks like some erosion has happened which is great for making mountains.
The reason for the vein like uneven appearance of the distance is because of how edge distance is accumulated. Like the Edge Transport sop the distance from a point to the goal point is counted up by travelling along the shortest possible path along the edges to the goal point. So the distance from point A to point B depends on the edge flow of the topology which create the variation and vein like appearance on a poly mesh.