newlib reentrant functions, when or should we use them ?

I've been investigating the function available in newlib recently, and I notice that there quite afew functions of the form

_printf_r

which of course corresponds to

printf

and according to newlib documentation on th net is the re-entrant version of the function.

My question is when do we need to worry about using these? Or do we at all under amiga os?

@broadblues
i think it's essential for multithreading programs
on multicore OS