I like to use tethered when doing workshops, but most of the time I wouldn't use it in a live model shoot since it proves to be distracting. The model is seeing the photos before they have been retouched, softened, cropped, etc and often what they see will not be what they expected. If you are working with a model who is perfectly made up and you crop exactly in camera as you want, then its a maybe. But with today's ultra sharp lens, even a made up model will often not be too enthusiastic about the details she sees.
Like others, I really like tethered for product shots, since then you can see if you have the DOF right which is often critical, especially on macro shots. I've have little demo page that shows the awesome difference that can occur between f2.8 and f22 on macro work. See this link to compare: