I haven't tried playing as an evil character yet, so I have no idea what it's like, or if it's even possible within the confines of the voice acting system.
I've played the game for 30 hours now, and I don't have a huge problem with it in general. The one time I DID have a problem was right off the bat. The idea that any realistic human being would:
1. bear firsthand witness to a nuclear mushroom cloud and the end of the world,
2. stagger into a cryogenic pod and get frozen for ~200 years,
3. watch his wife get MURDERED and his son get KIDNAPPED, right in front of his eyes,
4. emerge into a post-apocalyptic wasteland filled with giant mutant cockroaches and other monsters,
5. and then, after talking with his robot butler for two minutes, skip merrily down to Concord and start doing quests, tra-lala-lala-lala! oh, hey, what a nice doggy!
...is COMPLETELY UNBELIEVABLE to me. It completely KILLS any semblance of actual humanity on the part of this character and makes everything that follows entirely unbelievable.
They could have fixed it easily too. All they needed was one brief cutscene. After the character talks to Cogsworth, he staggers over to the wall of his house, leans against it, slumps down with his hands covering his face. Fade to black. Fade back in after an indeterminate amount of time has passed, good to go.
You know, something to show some kind of actual representation of human grief and suffering!
Instead, your character doesn't feel like an actual person. He feels like the protagonist of a video game. The fact that he adapts immediately to the Wasteland without so much as a moment of weakness, grieving, or any normal human emotion ruins him. It was a cool idea what they tried to do showing the world pre-armageddon, but it's killed by the poor execution.