Ask yourself this simple question - how many manual shift levers have you seen or heard of breaking off so that the shift knob was separated from the lever? I bet you that the answer is none or very few. When I said that, I meant all the cars that you know, not just Z32's.
Now think of the population of just Z32 - the population gets very small. Now, think of just the population of Z32 300ZX's with Stillen short shifters. The population gets even smaller, especially when compared to the total population of cars that you know. In other words, the population of Z32's with Stillen short shifters is a very small population of manual shift cars that you are aware of.
Well, in this very small population of cars, I have personally seen one broken shift level and read of two additional accounts of broken Stillen short shifters. I think the numbers speak for itself. Yea, you may say to yourself that there are only three failures that Glenn knows of, but again think of the numbers and the populations.
With proper design, material selection and then material processing/finishing, there should be no failures. Thank god it was only a shift lever and not something like a brake system.
In terms of performance, I like the shorter and the more positive shifts. There was definitely more notchiness and sometimes getting into first took more effort, but overall I liked the product. However, there is another shifter that I like more and that is what I currently have in my Z now. I have the C's unit from Japan and can say that this shifter is smoother and not as notchy as the Stillen unit.
In the end, the Stillen unit is fine in terms of performance, but is questionable in terms of reliability and longevity. Long ago, it was the only unit that was available, but there are now a couple of alternatives out there, that deserve serious consideration.