I'm sure the record companies love it, because it saves them so much money. They can pretty much have a vocalist sing one or two takes, as long as it's got decent attitude, and then have the computer get it in tune for them.
I suppose it's hard to argue the ethics of it, because if you're ok with copying and pasting an extra chorus in during the editing process, then that's basically the same thing: having a computer do what you didn't do yourself. I know some will say that's different, because it's just a choice that's made after the fact. But my point is that you can really only argue that autotune is unethical if you're a total purist and insist on recording everything (including the vocals) live to 2-track (or mono if you prefer) all at once.
Having said that, I'll say that I certainly hate it. It has undoubtedly contributed to the lack of professionalism in today's singers (and musicians in general).
It really is amazing to think that, back in the 50s and earlier, those people recorded those amazing performances completely live in one take. (I mean, they did numerous takes obviously, but the final take was one continuous performance.) The talent that takes is truly remarkable and, IMO, largely absent in today's world.