"What on earth does autotune do to an idiom where the usual performance style involves expressive microtonal glissandi all the time? You don't even need to go to Eastern Europe to find that, you get it in Gaelic song."

yeah, I've wondered about that. Any half-decent blues singer, too, is covering a lot more fine tuning than just bent fifths and thirds: there's usually some 'microtonal' stuff going on.

I can only speak for myself, but on some recordings I've been working on in Logic, there were a few moments where I thought I was singing painfully out of tune, and I tried adding a couple of 'cents' in Logic's pitch-correction plug-in. This was a tiny, tiny amount of digital pitch-correction, pretty much the smallest modicum that it provided. The pitch did indeed sound more in tune but I could hear a difference timbrally - I could hear the effect - and it was a difference I really disliked. It just sounded wrong, so I didn't use it.