My issue with them is the skill involved, it took me forever to learn to clean and I still can't clean what I can front squat. Also, for me personally the fast and deep knee bend contributes quickly to overuse and the rack position does the same to my wrists. About four or five weeks in to cleaning once a week and snatching once a week, I'm a mess. I want to learn them properly soon though, just because it's an awesome sport.
If you're already a weightlifter, they're a great tool. I'm just not convinced learning them is worth it for an athlete just for SandC purposes. Power variations, sure.