This has actually become one of my favorite mods as it "can allow" (with the highest density settings) structures that give you that "mine-shaft" feel. Combined with other mods (like ones that put ore everywhere and ones like Ore Chaos that intermix the ores) you can create the feel as if you crash-landed on a rocky asteroid or comet(when biome snow only).

I love that mining doesn't have to be cheap and easy and laying right there on the surface and the behavior that mining serves a purpose of creating fun tunnels and chambers that you can "suspend disbelief" and pretend is a cut-away of underground/inside-mountain areas (if not the entire map).
Regards,
~B