Considering the few characters I've played.
IA: I'm midway through Act 3, and I agree that it's a bit *** on the massive scale. However, and I know I'm probably alone in this, I didn't care for Act 2 at ALL. Because of this, I'm going to have to go with Act 1. An epic villain and a sadistic choice with a story that doesn't give me the personal creeps? Yes please.
SW: Act 3, by miles and miles. Yes, there was a choice that should have been available, but my SW would not have taken that choice, so the Act overall worked well for her in particular.
SI: Ok, I know this is weird of me, but I really liked Act 3, even though it has some significant similarities to IA Act 2. I think it has a lot to do with the characters I played. My mellow SI had an easier time with
Than my headstrong freedom-loving IA did.
Consular: I'm only to Balmorra, but I prefer Act 1 to Act 2. Act 1 just felt more personal, at least so far.
Every other class still needs to get out of Act 1.