Sorry about the delay in responding. While I do occasionally check the list archives, I'm not currently subscribed to this list.
I guess not alot of people use the piece tracker, else someone would have reported the bug long ago. I find it very useful for exactly the purposes outlined in the documentation. Probably the most typical use I make of the tracker is when setting the filter to a specific player's games within an ECO range playing white or black, to see where that player likes to place a specific piece or pieces for a given opening line of play. For example, I might be curious about where Paul Morphy liked to play his Q and QB early in the game as White in the Evan's Gambit. (Actually, that might be a bad example, since you really need a much larger sample of games than what we have for Morphy.)
Interesting insights might be had by using the tracker side-by-side with the tree window (per the documentation). The only statement I would take issue with in the help docs is with regard to the relative suitability of the two tracking modes: "% games with move to square" vs "% time in each square." I find both of these modes equally useful, the former moreso in the opening... the latter moreso in the middle game.
My real interest in the piece tracker, though, is as one of many features (both existing and yet-to-be implemented) in Scid which will be useful as an assist in training an intuitive neural net. The "footprint" or "pattern" assembled by the piece tracker, with the ability to vary and slide the window, can serve as an easily-tuned stimulus to the net during the learning process, especially when training along a specific opening line.