If you tuned into the Jimmy Kimmel-hosted American Music Awards, on top of that of Montreal T-Mobile spot and a wiseass JT-via-satellite, you might have caught Georgia country crew Sugarland and Beyoncé fiddling through a bluegrassy "Irreplaceable." Sugarland's been doing the cover in concert for at least six months, but never with Beyoncé. Which explains why Sugarland vocalist Jennifer Nettles ...