Xtingu (aka the IJG's Jill Knapp) has a solid appreciation here.
As I get older, I find myself on a somewhat desperate search for more and more remarkable music. I like a lot of what's out there, but I count myself lucky if I discover, in any given year, a handful of artists whose music compels me to take advantage of my CD player's auto-repeat functionality. Sumac was one of that rarefied crowd (for me) in 2006. And I'm still in awe.
If you've never heard her, be warned that you will probably either love her (as I do) or think she's just awful. This is not the music of moderation.