Personally, I think they are a fantastic idea on the beach for some vehicles. I don't own a set and have never needed a set. (In saying that, next time up the beach, guaranteed to get stuck big time.)
We do a lot of beach camping, and see a lot of people stuck. My vehicle is light, has plenty of torque, wide non aggressive tyres (no doubt that comment will cause debate, arguments and tantrums) and has ground clearance. My trailer is light, has wide tyres and also has ground clearance. Most vehicles now do not.
Most vehicles on the beach do not have any of these features. They're usually heavy vehicles, loaded to the hilt, heavy trailer in tow, with 185 R 14 tyres with 60psi in them "cause they looked flat" and a drawbar clearance of around 300mm, on a paved road. In this situation, they're great. A pair under the rear tyres gets the arse up out of the sand, which in turn lifts that sunken draw bar out of the sand, instead of it acting like a giant plough. A winch or strap wont lift the arse of the car like those orange things do.
Heavy vehicle, heavy trailer or low clearance, I reckon they're brilliant.
Shane.