I've been thinking about buying one of these but I don't know if they are just a gimmick. Also, if they genuinely work well how good do your bits need to be in the first place to be worth sharpening?

Even if you're only an occasional DIYer, there always seem to be holes that need to be drilled and screws that need to be driven. So it's no surprise that a cordless drill/driver tops the list of must ...