According to the wiki, since the patch you can open the shortcut from the other side without being in the covenant. Not sure if this is true or not...
Well worth it imo as it cuts out the whole of LI (those annoying dinos). The shortcut opens below where you beat the Firesage Demon and takes you out behind the Titanite Demon, just before the Bed of Chaos fog door.
Not sure if that shortcut is worth unlocking, though - from what I can see it leads to just outside the room with the Firesage Demon (who I've yet to beat).
30 Humanity very well spent imo