I recently became a PoSI and decided I was invested in the game enough to try a couple Fate-locked storylets. I really enjoyed Trade In Souls, but it reminded me of several options in early storylets locked by the reward items. The Loquacious Vicar, and someone in the University, I think. Even when I was trying to get my soul back from the Affectionate Devil,(found it in a Bundle of Oddities, go figure.) the Trade in Souls completion would have opened doors.
I’m waiting for the Rooms Above a Bookshop card to come up again so I can flash my new item. I can’t say I regret waiting this long before deciding to buy some NEX, but I feel like I’ve missed out on having the unique item reward earlier for more unique options in early storylets.
I don’t know about the other fate-locked stories but, as far as I know, the Soul Trade is the only one that ties into early content. It is still useful as a POSI, especially the side you have chosen. The last option on the card that turns up can be quite beneficial:)
For new characters/players I would definitely recommend getting the Trade in Souls as early as you can. Before the Loquacious Vicar, if you can afford the extra Nex for the option in that story, the University option is useful before you are POSI and the Soul Trade does tie into some other stories as well, most of them fate-locked as well though. . edited by reveurciel on 9/14/2014