I do agree that one's own character should be voiced.
In fact, it was the first thing that I noticed and surprisingly also the first thing that my girlfriend said about the game.
While I can see why some people won't like it, for many people this would immensely enhance the experience, and there could always be an option to disable it for anyone who really doesn't want it.
I understand that it would also take some time and cost more money, but looking at the success of the game in relation to what Swen expected, I'd imagine that this wouldn't be a huge issue anymore. It's also something that would happen, for the most part, independently of bugfixing and the addition of missing or new features.
This game will be around for a long time and for many playthroughs, so I think it would be absolutely worth it even now after release.
