What do you need the 3rd party account for? Such things are usually a deal breaker for me.
That's what I don't like about it. It seems they store your character and save file online like in an MMO, maybe to facilitate multiplayer, so that players can join each others' games at any time, but if you just play it in single player mode that seems like a very weird design decision. You only need an e-mail address to sign up for that account the first time you start the game and afterwards you don't see anything related to this account again - not sure if you're logged into it automatically behind the scene or whether it's not even necessary and they just wanted you to sign up for their forums - but I guess there's no guarantee about what happens to the game if any support is cancelled and the account servers are shut down, too ...
I'm playing through the game right now and when I'm done I'll probably never replay it, so I can live with that thought, also seeing that I didn't pay that much, but I can definitely understand if that's a deal breaker to some. Made me hesitate as well.
BTW you might also have a look at Ember
(did I already mention this?).
Never heard about Ember before, thanks!