I switched to SpamAssassin from PureMessage and was accustomed to the GAUGE 
header tool in PureMessage.  It's similar to _STARS(*)_, but adds one star for 
every 10% probability over the threshold a given email has.  (PureMessage uses 
probabilities instead of SA scores, but they're basically the same.)  That means 
that if you count everything over 40% as spam, messages at 60% will only get 
'**', and even the spammiest of spam will only get '******' instead of 50 
asterisks.  This is much friendlier for rewriting the subject, so I added a 
simliar functionality, called _GAUGE(*)_, based heavily on the _STARS(*)_ 
function.  The diff follows:

--- Mail/SpamAssassin/PerMsgStatus.pm.bak       2006-08-03 13:52:55.000000000 -
0500
+++ Mail/SpamAssassin/PerMsgStatus.pm   2006-08-03 14:24:02.000000000 -0500
@@ -1230,6 +1230,13 @@

             AUTOLEARN => sub { return $self->get_autolearn_status(); },

+           GAUGE => sub {
+               my $arg = (shift || "*");
+               my $length = int($self->{score} / 10);
+               $length = 5 if $length > 5;
+               return $arg x $length;
+           },
+
             TESTS => sub {
               my $arg = (shift || ',');
               return (join($arg, sort(@{$self->{test_names_hit}})) || "none");