Honestly, I wasn't crazy about Leliana at first, but her DLC turned me around. I wouldn't be crazy about someone like (a much younger) Elthina, or even Petrice, but so far we haven't seen Cassandra's full feelings about the Maker and the Chantry. If she's open minded and doesn't hate mages irrationally, I would give her a chance.
But just from her appearance in DA2, I like her looks, accent, and demeanor (bossy, no nonsense, not unnecessarily cruel while interrogating Varric...). That may change when/if we meet her again, of course, but out of the characters we met in DA2 who are possibilities as party members and LIs, she stood out the most to me.