Sometimes conversations are less like arrows and more like trees -- few points, lots of branches.

I think his point was: you really should read about dtrace, esp. how to instrument user programs (without instrumentation).

Err, if you already know the memory map of the functions inside a process image, then understanding the call stacks is trivial for any debugging or performance tool - on any platform. This does not require any instrumentation. And if you're reverse engineering, then dtrace is the wrong tool anyway. So, can _you_ point to any common use case of dtrace where the probes aren't already present in the kernel/libs/user code?