I use dof preview all the time on all my cameras.
I will admit it took me a bit to get the technique to be useful but it does help me on slr's where the lenses are always focussing wide open.
It's most helpful for me when shooting quickly and I need to make sure what I want/need will be exceptably sharp.
It really helps when shooting groups of people that aren't all arranged on one focus plane. Helps to get the best hyperfocal distance so all faces will be sharp enough.