Not worth it???? Are u insane? Ignore this person & all they speak, if you want to have a decent run with the game, it is more that worth it. I'd strongly advise getting them all, you paid for the game, get everything out of it. Max the Grid & ur stats & challenge the Dark Aeons, once you max all the dark Aeons sans Magnus Sisters become a breeze, Penance is 54354657876 times easier than Dark Magnus Bitches.
But yea, they're 'not worth it' if you plan to end the came in -30 hours & waste the majority of the game, but strongly consider it if you plan to max the game and greatly extend your playing time.