I have a lot of customers running these on their pro-touring muscle car applications with 500HP or more at the rear wheels, about where the Tru-Trac's seem to become increasingly unreliable. They work great for high traction environments such as road racing, however I don't have any off-road (dirt) experience with them, so I'm curious as well. I've talked with them at SEMA last year and the guy I was talking to didn't have much dirt experience either, at least not outside of rally racing, so he couldn't really answer many of my questions.
For similar performance, there have always been alternative helical torque-biasing traction devices to the Tru-Trac, but rated for higher HP applications, offered by companies like Quaife, Torsen, etc, however their costs are right up their with the Wave-Trac units at about $1000+.