We tested out our gear driven single-speed 6 CIM 8WD for the first time last night and loved it -
http://youtu.be/pQ6TMzGwV6U We'll be running a similarly designed drive this season with a 2 speed shifter incorporated.
Note that this frame is larger because we plan to use it as a test bed robot for seasons to come and it will double as a T-shirt shooter drive base.