I had those in Rochester on the xtrerra and LR3 and was also impressed. Then I moved up to Duratracs and even more impressed for an AT tire...here is a pic showing spent grabbers next to new duratracs:
I really like the duratracs, they have been superb for my needs and really suit the car.
Wear rate can be hit or miss, I know one D3 driver who has wear rate of 5,000 miles a mm. My wear rate seems to be 2-2,500 miles a mm. What is kinda annoying as I'll need to bin mine this summer but he will get a few years from his.