Dislike
Anders: Anders was too one dimensional and I really felt that he was just a dead weight, sprouting off a lot of nonsense that I really got tired of hearing very quickly. The fact that he is the only healer in a non-mage Hawke game is just annoying. In the end I was glad that I got to kill him, because I really couldn't stand to look at him after his actions. I just wish you had been able to kill him before he became a mass murderer.

Carver: I've rarely seen a more annoying brother. He just kept whining and whining and whining for no reason. Just by saying Hello to Aveline in the first scene, he got all rivalry. To betray his siblings (even if one is dead) by joining the templars is just ugh. One more reason to support the mages at least!
Neutral:
Isabela: I liked much of Isabela's banter and her flirting. Sometimes she seems a bit shallow (very), but there are times where she shows weaknesses and you hear more about how come she has adapted that personality. She would have been in the Likes if it hadn't been because of her betrayal of you. She could have prevented a lot of needless deaths if she had handed over the artifact!
Fenris: Fenris is quite an emo prettyboy. He is very opposed to mages, which is fine at the beginning, but then it just grows annoying. He does have a compelling background story though and being betrayed by his sister is just sad.
Varric: Varric had potential to be a great character, but in reality he is one of the most bland characters in the game. Sure he has some great banter and some interesting conversations, but he really lacks a lot of opinion of his own, only rarely taking a stand on anything. Of course since he's your only Rogue (other than Isabella who will leave you for a while, possibly the rest of the game and Sebastian that you only get after act 1 and only if you have the DLC), I guess that might be necessary, but still it makes him seem like he's really not caring what happens at all with the world.
Sebastian: Interesting background story, great looks, he's got a lot going for him. On the other hand he is perhaps a bit too self-righreous at some points. It is kinda sad that he only seem to be to the extremes, not a middle road.
Like
Aveline: Aveline is just a great character. She loses her husband, but moves on with life, eventually finding another man. She has honour, integrity, strength of character and is the pillar of support that none of the other characters can be, because she has been there from the start and knows how hard it is to lose. I only wish that my male Hawke could have romanced her, because she is really the only woman in the game that could be his soul mate (Isabela too shallow and Merrill comes off as too naive).
Merrill: I was actually surprised by this character. Starting out she did seem a lot like a naive girl with no idea what she was doing, but as the game advance, she grows on you. A lot. Oh, she does blood magic, but unlike most other blood mages, she is capable of remaining good at heart. She is the light that shows you that blood magic in itself is not evil, it is the practitioner of it.
Bethany: Your sweet little sister, taken from you by the templars and forced into the Circle. She seems to agree to most of your decisions, but this is because you are the older sibling, the one she idolizes. She's just the type of sister that you cannot dislike at all, because you know she'd do anything for you, so you'll do everything for her. Without her it would be easier picking a side in the end game.