If anyone's interested, here's the perl script I wrote to check through a .pwf file and print the names of any users who are also using their username as a password. It's not documented, but I guess that'll be a feature of version 2.0.

while(<STDIN>){
        chop;
        next unless /^(.+):(.+)/;
        my $name = $1; 
        my $pwd = $2;
        my $salt = substr($pwd, 0, 2);

        if (crypt($name, $salt) eq $pwd) {
                print "$name\n";
        }
}

This iterates through whatever's coming in on stdin (so call this like perl foo.pl < bar.pwf) one line at a time. It chops the newline char off the end then skips the line unless it matches the pattern of one or more characters then a colon then one or more other characters. It then checks if the username encrypts to the encrypted password. If it does, the name gets printed to stdout. ta da!