I've seen them advertised and looked at a few brands the last time I was in PetSmart. My cat is pretty placid and lets me hold her on my lap, like a baby, and trip her nails. Also, she was declawed, she's nearly 17 and it was required for cats in my apartment complex, so it would only be her back claws and she does very little damage with them.
I did think they looked cute, like a manicure, but was afraid they wouldn't stay on (which seems to be a realistic worry.) I hadn't thought about a cat trying to eat them. I've noticed my cat, when grooming, sometimes curls her front paws to be bottoms up and does a biting/pulling maneuver with them. I would think the claw covers might be a target for this kind of treatment.
