A proper fix requires some kernel hacking, but the work around is relatively painless. One need only add to /etc/modprobe.d/blacklist.conf the usbhid driver, and then add the bcm5974 on a line above usbhid in /etc/modules. This will prevent the usbhid driver from grabbing the synaptics touchpad before the proper bcm5974 driver has a chance.
You wild, beautiful thing. You crazy handful of nothin'.