It's useless in the city or densely populated areas. It's great on the open road, e.g. in the south western US, where you can drive in a straight line at 70mph for several hours without braking at all.

In that case your right foot thanks you for cruise control.

Back when I did more longish drives on thinly traveled roads in the South, I used it more. I've gotten out of the habit of using it because in the Northeast, even in rural areas, there tends to be too much traffic for it to be really worthwhile.

I actually like cruise control, since it's use case is very specific, and always works: keeping a certain speed.