Thanks for your answer.
So if I need a somehow complex design, using more than one arduino is the solution? Let's think of a R/C vehicle: one arduino would be the brain, one for "the legs", one for the sensors? They could communicate via their I/O?
Also, and completely off-topic: is your nick, "AWOL", originated from where I think it is: a military school? Because it's an acronym we know very well here