This year has been going very well for us. We think we are about a week to a week and a half from a fully functioning robot and...
We have turned into a moth that can't stay away from the little green light.
http://www.youtube.com/watch?v=xx1p7XGtWFE
That is our 2006 robot fully functional and tracking the light. We have made several circuits of our computer lab since we got it running. It will back off if the light moves too high and will move forward if the light gets too low. The driving has also been integrated with the light so that we can translate sideways and forward/backward while still facing the light to make it easier to place tubes during normal play.
This year's bot will have an almost identical drive train so updating the code will involve some gain changes but otherwise be "effortless".