I like Triss. She is more than a card to collect - she has a mind and an agenda of her own. I appreciate how, even though it's heavily implied that she and Geralt had a relationship in the past (I haven't read the books, but the journal isn't exactly subtle about it), she doesn't play that card and lets Geralt decide by himself. She also acts reasonibly respectful if you take Alvin to Shani instead of her (i.e. doesn't become a jealous hydra and banishes you from her house - that disappointed me about Shani). I only wish choosing her or Shani had a bigger effect in the storyline; you get almost the same scenes and even the same lines.
Hey, she is in a stable, monogamous relationship! ;) I agree Carmen is awesome, and "Beauty and the Beast" is one of my favorite quests in the game.