Calculators come in handy long after Calculus class

That's right. We all dreaded math and calculators...never thought we would use one again. Besides figuring out those taxes...which is another topic in and of itself. However,
there is a calculator out there that is made just for us! And it
isn't hard to use...I promise!

This wonderful, magical calculator I am referring to is of course the Depth of Field Calculator. This handy little online calculator will tell us what our maximum depth of field
is depending on our camera. This ensures us the most sharp and clear
pictures no matter what type of camera we are dealing with.

And as we know, this is about more than just what we see through our lens. This definition clearly states what goes into getting the most sharp pictures:

Image clarity or sharpness is not just a matter of focusing a lens on the subject. There is an area in front of and behind the sharp focus
plane that is also sharp or clear, and the extent of this area
changes, depending on the focal length of the lens, the focusing
distance, and the aperture used. This three-dimensional area of sharp
focus is called depth of field.

Lonely Planet Landscape Photography: A Guide to Taking Better Pictures,
Peter Eastway, 2005.

You can get to the calculator by visiting http://www.dofmaster.com/dofjs.html.

Who has used this and how did it help or not help you? Would you recommend it?