I tested Lucid yesterday, there aren't old touchpad problems, the sensitivity is good, so the synaptic package is now useless.
Dragging your finger on mouse pad from edge-to-edge moves the cursor about 70mm vertically, but about 25mm horizontally?
Before installing synaptic package yes, when I made a circle with my finger on touchpad, mouse drew an elipse, but after installing package, it makes a circle.
Maybe your problem is not sensitivity but acceleration ? With me, when I dragg my finger slowly, mouse cannot go from edge to edge, but when I dragg it faster, mouse does it.