Are you sure? What problems are you having? Here's the snippet from the code that translates smart-quotes:

$s =~ s/\x93/"/g;
$s =~ s/\x94/"/g;
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And here's how I've modified the core demoronise sub:

sub de_cp1252 {
  my( $self, $s ) = @_;

  #   Map incompatible CP-1252 characters
  $s =~ s/\x82/,/g;
  $s =~ s-\x83-<em>f</em>-g;
  $s =~ s/\x84/,,/g;
  $s =~ s/\x85/.../g;

  $s =~ s/\x88/^/g;
  $s =~ s-\x89- °/°°-g;

  $s =~ s/\x8B/</g;
  $s =~ s/\x8C/Oe/g;

  $s =~ s/\x91/'/g;
  $s =~ s/\x92/'/g;
  $s =~ s/\x93/"/g;
  $s =~ s/\x94/"/g;
  $s =~ s/\x95/*/g;
  $s =~ s/\x96/-/g;
  $s =~ s/\x97/--/g;
  $s =~ s-\x98-<sup>~</sup>-g;
  $s =~ s-\x99-<sup>TM</sup>-g;

  $s =~ s/\x9B/>/g;
  $s =~ s/\x9C/oe/g;

  #   Now check for any remaining untranslated characters.
  if ($s =~ m/[\x00-\x08\x10-\x1F\x80-\x9F]/) {
      for( my $i = 0; $i < length($s); $i++) {
          my $c = substr($s, $i, 1);
          if ($c =~ m/[\x00-\x09\x10-\x1F\x80-\x9F]/) {
              printf(STDERR  "warning--untranslated character 0x%02X i
+n input line %s\n",
                  unpack('C', $c), $s );
          }
      }
  }

  $s;
}
[download]

I didn't really care about the other stuff (such as bad html or unicode) - just translating the known cp1252 misplaced characters into something reasonable.