I like 'em. Started using them on gills I use for bait, and it seems like I was getting more hookups and holds with the sickles, so I've started to converting to them for my crappie rigs too.
I tend to think the hard angle in the back of the hook vs. a curve in the back of a normal hook will hold the fish on better. May or may not be true, but that's why I've been trying them out.
Vector