For programs that produce real output (slapcat, ldapsearch) this
be true, but for those that don't (slapadd, slapd) I totally disagree.
Stderr is for errors, not chatty progress or debug messages. I always
hate it when the error messages gets burried in lots of noice.
My preference is to have progress and debug messages on stdout, enabled
by options or at least possible to disable by options. Real output must
be possible to send to a file specified as argument, to separate it from
the progress and debug noice. Stderr is for error messages, and
possibly out-of-band messages.