I think it would depend on the definition of use. I lurk in /t/newtribes a lot, and like having it as a quick click up there, but I'm not sure lurking could be considered as using from a programming perspective. I would rather the ability to set the tribes I see up there, and the remaining being filled by my most "used"!
Why not have it how it is, or 'most used', but allow you to 'pin'(probably a bad choice of words) ones of your choice to the top. Any that aren't pinned in this way fall back to the normal sorting.
Yeah! That's ideally what I would like to see, something that's more customizable.
I agree that being able to set the tribes would be nice! Most of them would probably end up staying the same as they are now, but having shortcuts to less common tribes would make visiting them a bit easier and I feel that I'd end up visiting them more frequently. I know it's only one more click to see my top tribes, but I definitely rely on the top bar a lot more than that window.