I am struggling to get _both_ my touchpad and external usb mouse working
correctly with the same xorg.conf (included below).  In particular, if there
is a generic mouse entry with device "/dev/input/mice" then clicks on the
synaptics buttons (both buttons) are always counted twice.  Probably they
are sent to the X server both by the synaptic device and by the generic
mouse.  If I remove the generic mouse stanza, then the synaptic clicks are
interpreted correctly, but of course external mice are not detected.  If I
put in generic stanzas for /dev/input/mouse0, /dev/input/mouse1 etc., the
external mouse and touchpad work correctly, but only if the external mouse
was already plugged in when the x server was started. If I plug in the mouse
when the X server is already running, then the server ignores it.

By the way, this exact same configuration worked perfectly on another laptop
(an ASUS A6K), while it does not work on the present one (and Acer
TravelMate 6593). While it is entirely possible that I missed some obvious
configuration option which fixes my case, I did try everything I could think
of (GrabEventDevice does not work, for example, and trying to divert
"Repeater" to "/dev/null" had no effect.