In mud they are terrible. I ran them in 285/70-17. They were awful in the mud but they were VERY smooth and quiet on the road. They are also good for dirt and general trail driving. Just stay away from the soupy stuff. Really great tires if you spend 95% of your time on the pavement and only hit trails on selected weekends.
I got 26,000 miles on my set before selling them, and they had 5/32nds of tread left at that point. So they would have been worn completely out by 40,000. Granted, that was on a Ram 1500 so it was a heavier vehicle.
~Lots of modded Jeeps and a Toyota 4Runner~
My favorite quote from the press release.. sad but true: "Chrysler claims its products, especially the Jeeps, can handle all sorts of terrible conditions, churning through muddy swamps, climbing mountains, and crossing rivers. Turns out they cannot even handle a car wash."