Couple of things on Kat:
1) When there is no pressure she is quite good. Very relaxed. She puckers up when its time to sing for votes.
2) My wife (trained singer) was yelling at the TV about how horribly off-key Meatloaf was. Then she raved about how incredible Kat was to stay on key while he was murdering the song.
Agree with you on both points. I've seen that in Kat all season -- she was invariably much better on results night, when she didn't actually have to sing for votes. Too bad; I think that cost her.
And I agree with your wife -- it is incredibly hard to keep going correctly when someone right in your ear is way off in another dimension note-wise! That was part of why I gave such props to Kat for that performance. As I said, if I'd seen that kind of performance from her earlier on, I might have had to change my votes a bit. (Though I'm still glad Taylor won! :)