It may be obscure, but I have it - though I have never played it or ran it, so there is that.
I like the rule because it is a start down the path of the type of rules I prefer: one in which how well you do really matters, and not only when you get a "critical." An easy way to get this point across is by saying that I like Rolemaster more than D&D. (Just look into RM if you don't know anything about it and you will understand pretty-quick.)
But RM combat is all about the criticals! (and the fumbles!)

Cheers!