I've long been as anti-handcuff as they come (though in part because the main league I played in had open waivers). This year I joined a league with standard waiver rules. I drafted Charles and RBush, then added Joique, less as a handcuff as because I wasn't really sure how the Detroit RB situation would play out. Luckily, that move panned out (including allowing me to sub in Joique last minute when Reggie was out in Week 3), but in the meantime, it never occurred to me to add Knile Davis, mostly because there was no way I would have started him over my backups (FJax, and later, Andre Brown).
Just before the trade deadline I traded both backups for Gronk, and there was absolutely no one decent on the WW. At that point, it finally made sense to pick up Davis. If Charles goes down, I'm probably screwed no matter what, but at least Davis would see a bump in value, whereas anyone else I picked up would be just as lame as they are now.
So in that narrow circumstance, it made sense to pick up a late-season handcuff. But generally, I agree that they're way overrated.