Had mine a few weeks now but havent had too much time to play with it due to exams. So far I've managed to get an arduino sketch going and a python script to upload temps to cosm.com Next step for me is to work out how to get the arduino to control my beer cooler with a relay and PID function.... And then maybe modify my script so it picks up the Setpoint from another feed on Cosm.com - this would allow me to avoid setting up a web server/page myself, which is a bit beyond me. - Hence why I'm so interested in BrewPi!!
CAN (and it's little brother LIN) are indeed bus alternatives. They are lower overhead than USB. They aren't quite as good for long distances as some other alternatives.
For the relative simplicity of this project, I think LIN would be perfect. Volvo uses it to communicate with every electronic system (down to the rear view mirror) in its newer vehicles. I think it would be sufficient for brewing. Plus it is lower cost than CAN and USB.