Having looked at SIG magic, it's even more horrible, but the real thing on why to avoid $SIG{__DIE__} is when you mix die and eval. If you can live with your $SIG{__DIE__} handler getting called even when the program doesn't actually die, then I think using it to copy the message to some logging/notification is OK.

$SIG{__DIE__} = sub { die "[".gmtime." UTC] (PID $$) FATAL ".shift };

if( !eval {
    die "Whoops";
    1;
}) {
    print "Error reading config file, using defaults\n";
    ...
};
[download]

Update: Upon reading your node to completion, you already mentioned the case I'm pointing out, sorry.

Outside of that weird/potentially confusing interaction, I simply wouldn't want to put complex logic in a SIG handler because something already went wrong, but again, copying the message to syslog or whatever doesn't seem too bad.