Not sure if I'm posting this in the right place lol,
Done the Above Hack, Here's how!
(Note that you CANNOT use this with the original hack)
OPEN:
wp-admin/options-general.php
FIND:
<tr valign="top">
<th scope="row"><?php _e('Membership:') ?></th>
<td> <label for="comment_registration">
<input name="comment_registration" type="checkbox" id="comment_registration" value="1" <?php checked('1', get_settings('comment_registration')); ?> />
<?php _e('Users must be registered and logged in to comment') ?></label>
AFTER ADD:
<label for="users_can_register">
<input name="users_can_register" type="checkbox" id="users_can_register" value="1" <?php checked('1', get_settings('users_can_register')); ?> />
<?php _e('Allow User Registration') ?>
</label>
Then in each blog under:
Options > General
You will find:
http://bloggi.org/images/bloggi-userscanregister.png
(See ScreenShot)
I think this would be pretty cool if added as a core feature... I know i'd like it to be there :-p