I fooled with them many years ago. They worked, but no better than basic eggs. I think if you are trying to use a small bait (dime sized) and your eggs don't hold together well, they'd be worth the effort. I use a larger bait, usually no smaller than a nickle, and use a cure that results in pretty durable baits, and so don't have any need for them.

They certainly help conserve bait, if that is a concern.