I feel like a proud papa. At around 11:00 AM today Rockhopper took it's first steps. I don't have any sensors hooked up yet but I wrote a quickie program to just turn the motors on for 5 seconds and go straight and it moved across the floor for a few feet completely under battery power and while I was logged in via ssh over the wireless net. I do have one minor bug where it doesn't turn both motors on at the same time. I have some "optimization" code in the motor routine that prevents it from doing anything if the speed has not changed, I think I have a bug there. Shouldn't be too tricky. Once I have that fixed I am going to write a program to drive it around via keyboard commands.
So far I am very happy with how long it runs on the battery. I had it booted with wireless ethernet for over an hour last night on a battery pack that wasn't even fully charged. Granted that was without any sensors and I expect the IR rangefinders will pull a bit of current but this is very promising.