Barbara, Bill . . .
Thanks for the kind comments. I bought the DP3 for just such work, and I'm making progress getting it dialed in.
Bill, yes... focus stacking is a pretty powerful concept for macro work, but as seen here has application for extending the DOF while keeping the aperture of the lens at its sharpest spot in more normal work. Many landscape photographers also do stacks to get near ground / background extended DOF.
I've found Helicon Focus to work best for me, though Photoshop has this utility as well, and there are other software products out there for this.
There is even a "freeware" available that you might want to check out: http://zerenesystems.com/cms/stacker/softwaredownloads
Here is another example that I've posted before (taken w/ a900) that illustrates what can be done with landscape work. This image was shot at 200 mm on a FF camera. Five shots were made, each focused on one of the trees moving front to back. Stacking made possible a sense of DOF that would not be possible at this focal length otherwise:
Sequoias - Mariposa Grove - Yosemite
end digression /