Check this out:
http://www.gpsvisualizer.com/misc/NetStumbler.svg
Non-interactive GIF:
http://www.gpsvisualizer.com/misc/NetStumbler.gif
It took me a while to assemble that from Dutch's exported data, but it's an example of the kind of thing that COULD be done with complete data.
I actually started doing it because I wanted to see how the "summary" points were calculated. It looks like it might try to mark a point near the center of the points it collected from a particular base station, but it's not 100% predictable.