My neighbor buys the Terra Grapplers for all his trucks, he doesn't off road that much, but they do they job when he does. They are good A/Ts if you do a lot of on-road driving as most of us do. They will last quite a while too, if I'm not mistaken.
I have the Mud Grapplers on my truck, and I am ususally on pavement, which is a bad combination, since they wear real quick on the road for most people (except jeeps, which are very light). But they are exceptional off-road. The only thing I have heard is some experience some chunking. I wouldn't know, because I'm in Florida, and most of the stuff out here is softer. They are loud, btw.
I think I might try out the Trail Grapplers on my next go around, we'll see.
I have spoken to a guy that said the Dune Grapplers are good on road, but he had never taken them in the sand, so I don't really have much to say other than they look kinda cool.
Those are the only Grapplers I've had and experience with. If you're thinking about getting some, I'd say go for it. You won't regret it.