UserSettings should also be set/get from cookies, so then guests can change them. And for logged in users it would keep the cookie and the db setting in sync.

So to set;

href="<?php echo $this->Setting->disp('my_setting','new_value'); ?>

function disp( $setting_code, $value ) {
echo regenurl($this->classname.'_'.$setting_code.'='.$value);
}

Or whatever.

This would be used for the gallery plugin's display modes, as they are customizable by the user/guest to the blog.