I've read the iroks wear out fast, but i have a few thousand on mine on/off road ant they still have the little ticklers on the sidewalls. Very very little wear.
In mud, they work great. In snow, they hop BAD. Turns the rig into a chatter box. Ice, they seem to stick very decent for no sipes. Sand, they hop as well. I have no blocks on the truck. It could be my suspension setup, but i dunno.
Overall, I really really like them. Mine are 36x13.5x16 and they were under my k5, now theyre under the SAS'd burb. They clean decent and are surprisingly quiet. Even at 75+mph.
Have you looked at Goodyear Duratrac?