>Sure, you can force a certain note, but it sounds artificial.
But it doesn't need to. They don't have to do auto-tune in discrete steps following a set scale, it could be (as far as the human ear is concerned) done in an analog fashion.
The technology will improve until you don't even notice it. It may already have done so, with the only auto-tune you notice today being deliberately worse than necessary for effect or simply the result of cut-rate sound engineering.
Which makes me wonder... can you get a mic with built-in auto-tune for home karaoke yet? I sing like a cat being strangled, I could use one.