I'm with John...it's fun in some applications/situations. Curious, are you using a vari-nd just for stills outside or for video?
I bought a vari-nd for outside video and I did some test with stills and it took some IQ from my stills, but for video it worked well. I'll have to find if I did some tests and posted them and come back and link it here.
I find that Lee or Hitech ND or GND filters (4X6) are the best when it comes to landscape stills, preferably GND filters.
I'm actually using it for stills. I don't do the video thing. It was very much an impulse buy since the price was low and it is a nine stop variable. I've been wanting to play around with one without the usual high price for the better quality ones. Getting a good GND is on my list of items to pick up in the near future.
I believe this shot was around 2-3pm at f-18, and about 3seconds with the filter cranked to full.