I've been using CSS off-and-on pretty much since the first browsers started supporting it; I too struggle to see the point of the frameworks I've tried. There's only one thing I have trouble with: maintaining clean & tidy CSS once a site grows beyond a certain point. Details get changed, which causes classes, etc. to be forked, rules don't get deleted because it's not clear if they're really unused, etc.

Do you have any advice for dealing with this? I feel there ought to be some way of semi-automatically "refactoring" style sheets, or keeping them compact and neat to begin with, but I haven't yet found it.