I've used them. They work the same as double stick tape. You apply one side to your couch while the other side is sticky side out. It worked for me, my cats instantly stopped scratching the sofa and haven't done so since. But beware on what type of surfaces you use them on. I suggest cloth surfaces only (cloth couches, beds, etc).
Used it on my couch sides and edges, worked GREAT! Only had to use it for a couple of weeks, brought in extra scratching posts, and since then, she's never once clawed the couch!
Sticky paws was absolute h*** to get off of woodwork after it had been on there for a while.
A cheaper alternative is laminating paper. It's pretty cheap at Walmart. Cut it up to a convenient size and attach with double-sided tape. Use the removeable tape, not the permanent.