AUTO-LOGIN V3 is a little safer than V2.
V3 stores user's password as md5 encoded with time limitation.
If cookie is stolen by someone, he can't login after auto-login expiration.
This means that short expiration makes your site a little bit safer.
This hack is applied now.
$_COOKIE['autologin_pass'] of V3 is incompatible with V2.
Thus, you as a user enabling auto-login have to log-in manually once.