I just saw it for the first time, the day before yesterday. She was great! My wife actually brought her up, while reading about her in People Magazine, and was shocked that I hadn't heard of her.
For the one that was saying he thinks she a fake (really, she's not, it's BIG news), but says it might be due to the poor quality video, here's another link, to the same performance, only higher quality, and with the HQ (High Quality) button you can click for really high quality.
http://www.youtube.com/watch?v=RxPZh4AnWyk&feature=related Don't forget to hit the "HQ" button; it makes a big difference in the quality of the sound and video.