I've not worked with any singers that aren't, um, at my college doing music tech xD So I don't really know about that side of things, as I'm mostly just edited myself or a friend - usually myself. On a personal note though, I hate listening to my old takes when I'm recording - I like having lots that are all a bit different and then layering them up or cutting bits out of one and putting it in another or whatever, it appeals to me xD If you don't have the confidence to perform even if you think you might be a bit crummy then I don't know why you'd be in a studio anyway.
I don't like auto-doubling much either, tbh - I think that a live performance should be as live as possible, and if that means changing your sound then so be it. It's just a personal thing though, I don't think it's as much of a problem as auto-tuning.