We don't have any type of ranking system at our dojo, which doesn't bother me at all. We are a small club, so everyone knows I'm the newbie, and I've quickly figured out who the more advanced people are.
As far as self-satisfaction, I don't care about that. I didn't start aikido as something to conquer. When I think of getting belts, I associate it with conquering something. I get my self-satisfaction from conquering routing problems on our network here in the office.
Now, don't get me wrong - I don't think rank is a *bad* thing, just not something I feel *I* need. I wouldn't be opposed to wearing colored belts to show my rank.
A lot of people work better using a goal oriented system. The belt's give them a goal to shoot for. If that works for you then great. For me, I'd rather let my skills (or lack of them, as it stands right now) speak for me.