It follows the original storyline almost to the letter. Sadly, it's just not as good.
While Jaden Smith is undoubtedly 'one to watch', and while his comic timing is scarily like his dad's early stuff, he's just not right here. The original Karate Kid, Ralph Macchio, was puny, and his character was 16 and poor. Jaden's Dre Parker is recently arrived in Beijing, so you have to assume his widowed mother has a fairly good job. From the inappropriate number of topless shots, when Jaden grows up, his physique is going to rival his dad's. Also he's 12, and attending an international school - somehow the lack of grit makes the bullying that leads to his becoming the Karate Kid less believable.
That's not to say this is a bad film: the shots of the gorgeous Wudang Mountains, the fight scenes, the chemistry between Jaden and Jackie Chan, his onscreen mentor, and even the simple fact this film pays tribute to such a symbol of the 80s make it worth seeing.
But if you're expecting a new iconic mantra, 'wax on, wax off' trumps the new version every time.