I have no less than five version of this song on my iPod. I'm a tad obsessed with it. The sample is just hot - so catchy. In the Britney version, there's the iconic ping-pongy surf guitar, the bouncing chromatics in the background, the beat, those heavily processed soaring vocals. But no line detracts from any other; it's neither too chaotic nor too flabby. This song is layered so tightly it feels like abs of steel.