This is the original power window motor that provide motion control for the skateboard truck based slider:
It is likely to stay there as the main drive with timing belt/gear (still awaiting shipment from NY). The RC servo previously used, with the addition of another servo will later provide controls for pan and tilt (Still mulling over the design).
Variable speed is provided courtesy of a PWM controller and powered by a rechargeable 12V power drill battery.
I have tried this rig upside down and sideways (manually) with no problem at all. Many options yet to be tried out, including swapping out the 4ft rods with 2ft leftovers for a shorter compact version.
My test of the Tokina 11-16mm + 60D and Nano Flycam combo can be viewed at: vimeo.com/28930969
update: Slider passed rough test: vimeo.com/29420326