Wheeeeeeeeeeeeeeeeeeeee! The touchpad cursor is now flying across the screen, faster than ever before, I think. It must have been fixed in this morning's updates.
Edit: It was necessary to delete the /etc/X11/xorg.conf.d/synaptics.conf files, to get back to a sane level of cursor control. I looked at the changelogs for the two xserver-xorg updates, but I'm not sure that is even where the problem was fixed. In any event, both the netbook and the laptop are back to normal performance.