Have you played each character? If so, who do you like to play the most and/or the least?
Flavor and ability wise, Lem is my favorite. His ability to pull spells from the discard pile makes him a top performer. His ability to sing/perform to help his teammates if fun to role play. :)
So far, Seelah has been the least fun to play. It's great that she can add to ANY check, but the cost is quite high. Unless she's playing with a healer, she's almost as squishy as Seoni without the high damage output. For somebody wearing plate armor, that doesn't make a lot of sense.
Regardless of most or least, I am thoroughly enjoying this game. It's a lot of fun to play in a group, but it's nice that you can play solo too!
Valeros and Seoni have both been a blast to play. I love how Seoni can turn anything into a fireball... we have a running joke that the sages she keeps getting are covered in kersoine (seriously, she has a sage in her deck, and in over half the scenarios she ends up finding a second one.) Valeros is helpful in groups, and can swing for massive damage with his ability to recharge his weapons. Merisiel also is a great representation of a sneaky character, and she has a very unique playstyle.
Sajan is kind of boring. He's not weak or anything, playing with him has always been a bit repetitive, especially with 8/15 of his starting cards being blessings. Ezren has more options because of all the different spells available, but he's still kind of boring, and not very fun in groups since he doesn't have any blessings to help people out with. Might change a bit if he gets access to some of the later utility spells, but so far I haven't been too impressed.
I expect you'll have lots of different answers. Valeros is my favorite. Sajan is second.
Of the characters I've played, my least favorite has been Amiri, though I wouldn't say I hated playing her. And I haven't picked her up again in a while and think I understand the advantages of her movement power better now and would enjoy her more.
I haven't tried Lem, Harsk, Seelah, or Merisiel. Seelah appeals to me the least, but deep down inside I'm convinced it is because I fail to see her greatness.