Uh. The Thieves Guild in Skyrim is one of the worst written questlines Bethesda's ever done. It's like Skyfall. Fun and cool looking, but nonsensical.
I'm just hoping that the dialogue options we saw aren't what's actually in game and are subject to change. Deus Ex HR showed you exactly what the character was going to say. That should be done here. If the dialogue choices were representative and not poorly paraphrased, then they'd be able to stand on their own and be optionally disabled.
That'd please me.
A voice actor just seems like another stepping stone for homogenization, 'casualization,' and hand holding. I play Bethesda games for thousands of hours - part of what lends to that replay value is the fact that I can craft unique characters. A voice hinders my ability to do just that.