I would link to my writeup from my Best of 2010 list, but I'm not that much of a selfpromoter.
Waiting is far more than a simple dance song. It's the most emotional, emotive song she's ever recorded. It's gorgeous, and heartbreaking. Even though five people wrote it, it's maybe the only song that feels like it came from her; the interplay of the sorrow and bittersweet feelings of the lyric perfectly syncs up with the joyous of the music. Such a clever sample too. Almost genius.