Shadowheart is the only character whom I still dislike with 70 hours into my gameplay atm.
I hope they work on her a bit more, she is still a moody teenager.
Gale is okay, I think he could be worked on a bit more to make his character less generic. Wyll could use work like Gale does.
Astarion is my favourite companion, he's much more fun than having Shadowheart following me around(it was especially funny when you go knocking on the shed door in the Blighted Village XD!) He is definitely one of the more fleshed out companions <3.
Lae'zel is also pretty good in terms of character development. She is not annoying like Shadowheart, I just hope she's okay with me