As far as second (or is that third?) careers go, Britney has made a helluva comeback. Although her core audience is made up of people who remember her initial rise to success, followed by the up-again-down-again pattern of failed relationships, emotional breakdowns and performance flubs, the former teen idol has settled in ever-forgiving Vegas to reinvent herself once more. And she has done a bang-up job. Piece of Me isn’t a concert; it’s an opportunity for Spears to reenact her greatest hits with a gaggle of dancers and some high-end stage sets: “Look, there’s Britney in a ring of fire”; “Here’s Britney floating above the stage.” Some of the credit goes to Planet Hollywood, whose redesign of the phenomenal Axis Theater specifically for Spears has afforded her a brilliant platform from which to begin her new trajectory, but the achievement mostly belongs to Spears. She’s an older, sexier, more stable version of her younger self, with all the charisma she started out with.