I should have added wheels to the simulator a long time ago. It's approximately 3.9*10^3 times more fun now, give or take an order of magnitude.
The control system has also turned out to be much cooler than I expected. You just create objects like motors and controllers and arithemtic operations, drag them arround on screen, connect them, and you get a control system. It just occurred to me that this could be a pretty cool thing in its own right if it generated, say, PIC code. Hmmm.