Here is a company that we have been working with other projects outside FIRST. They put together a robot using their products and mecanum drive. It moves really nice. Watch the whole video. Check out their website. I wish we could use their products for FIRST. The C-rio does not take usbs well. If any body out their knows how we can incorporate usb for C-Rio, let us know. We use Phidgets in our underwater robots for the AUVSI Robosub Competition.
Here is their website with details and code
http://www.phidgets.com/docs/Mobile_Robot_(MURVV)