I consider Unit tests to be essential. People who don't like them, maybe they never tried to drive a value from them.

I also use-to consider them not important, but they have saved my as* so many times.

How would you drive a big refactor, without introducing new bugs - without unit tests?

With a solid test coverage, via a button click, you can conclude - how functional is your code base. Of course, not on the basis of weak tests.