I'm assuming there must be some kind of anti-rotation bars, if they over-rotated they'd tear the fender up pretty good.
I also can't help but think it might be tough on transmissions and power trains on those heavy full size pickups and Suburbans but probably just fine with a lighter vehicle like your Jeep. I would also think one might have to be careful about the snow packing up into the undercarriage and engine bay area. I might be tempted to close up the gap between the radiator and the engine with a skid plate or a shield of some kind.
I'd try to find out about overall maintenance costs, is anyone twisting off their truck axles or burning up their trannies for example?