I got the ARobot because I wanted to learn how to use the Basic Stamp II with something fun and less "sterile" than a simple test board. I am 52 years old and, like all boomer nerds, have been interested in robotics for as long as I can remember. I learned FORTRAN II D in 1968 on a 20K core (we didn't say "byte" back then!) IBM-1620. I was a systems analyst on "big iron" computers in the '70s; and since switching professions to the health care field have continued my computer interest as a hobby (I built my own ZX-81 machine in ~1981 and used it to teach myself BASIC for the first time).
I have accumulated the parts for all of your suggested apps (except I'm going with the Dinsmore compass, not the Vector; and IR rangefinding, not ultrasonic). I plan on something not quite so grand as the 501-C, but do intend to explore how rudimentary AI can be implemented with it. I also have an X-10 camera to mount with a fourth servo to somehow aim it.
For me, it's the process, not the (never) finished product that's the fun; and hacking the software is easier for me than the mechanical aspect.
I also have some vague plans to use an amateur radio 222MHz link somehow, but that's way off in the future.
Thank you for coming up with such a great product.