Without getting into all the details, I'm at a point now where I'm trying to do a brute force recovery on a WD 2TB 7200RPM drive using the photorec tool bundled with TestDisk in Windows 7 onto an identical WD 2TB drive. Both the source drive and target drive are new, good drives. One drive contains the image of a drive that failed (and hopefully other data that was overwritten when I attempted to clone the drive that was failing onto it -- doh).
However, the longer program runs, the longer the estimated completion time becomes. Presently there is an estimated completion time of 242 hours, and it has only been running for 23 minutes. I'm not sure if the sector value should be increasing or not, because presently it's hopping around 6200000/3907029168, but not really increasing or decreasing. It has also been stuck at 4471 files found -- and that value hasn't changed at all.

I could really use some help here and would be happy to provide more details. A google search provided some hope that PhotoRec will get out of this cycle on its own...