Alan, now you've got me curious.
I know there are tons of methods for position tracking, but what method do you use? E.g. what sensors, what algorithms (if you don't mind sharing

) and other such things... because from my experience, accelerometers aren't capable of accurate position tracking, but who knows, I'm hoping someone proves me VERY wrong.
Also, is there a benefit to a speed control PID? I mean, going straight, yes, but wouldn't directional control be easier with a gyro and joystick position?
Basically I'm asking for what all of you use PID loops for, because it's nice to know what's worth the effort in tuning.