basically, yes!  i've been working on my own, which used the turbulence and p-node together (i want the edge of the fog to be noisy too), but this is simpler.  the big problem i've been having is previewing.  that is, adjusting the hardness and location of the edge was difficult.  using the setup on a primitive helped me.  i'll be saving yours as well.  thanks so much, nghayward!