Actually my definition of "great" DOF is the ability to blur the background at will using wider aperture settings.
That is what I miss the most from my 35mm camera. Digital "prosumer" cameras have short focal length with resulting l-o-n-g DOF. This has caused them to be labeled "point and Shoot" cameras by the more snooty bunch that can afford those digital SLR's with removable lenses. In defense, however, many of these folks started with fixed lens digitals and are still very helpful to the rest of us. Pekka is a good example.
I know what you want. I want it, too. The ability to fill the frame AND blur the background at will regardless of subject or distance or light. There are prosumer limitations but, as I understand it, the work-arounds are possible with the PRO90 because of the 10x zoom lens.
Step b-a-c-k; zoom in (longer focal length), select portrait or wide aperture, and bingo! Full frame, can't see squat in the background, digital full frame picture thanks to the 10x zoom.
Am I right? (I don't own a Pro90, yet).
But the theory sounds right. Man, I hope I'm right because I miss short DOF so much.