Well, I can't say I was a huge fan of Vin, but I also didn't dislike her either. Whilst I understood where Sanderson was coming from regarding the paranoia, I did think it was a little overdone. Also think she was a little two dimensional, but that can be improved on over the trilogy I think. It hasn't stopped me starting book 2 though, which I'm really enjoying. Elend even makes fun of Vin's paranoia, so I think Sanderson must have listened to critics regarding Vin before writing the second book as she's much better.