I did use a pretty standard example there. Below is a better example. In that, I'm using a noise map to drive the inset amount per face. Houdini's Extrude tool allows you to optionally remove the front faces post-extrude, so you get the holes for free.
To drive the point further, once you have a per-element attribute, you can do pretty much what you want with it - obvious candidates are per-face colour, scale, rotate, extrudes, etc., but you can also use it to drive density if you want to scatter some objects on there, or if you're simming, drive per-face friction, bounce, mass, etc. You can also exploit the attributes for very precise selections, so you can group all faces that have a value of < 0.5 say, and then do a subdivide (for example) on only those. The sky's the limit really.