SERIES PREMIERE: Jennifer Lopez is one of the executive producers, as well as the best-known celebrity judge, on this dance-competition series, which promises a prize of $1 million to the most jaw-dropping dance talent, whether solo or group, and in whatever discipline or genre. And on American Idol for years, Lopez honed her ability to sound genuinely excited, while seeming to care genuinely, about the talent performing before her. That skill is evident even in the promos for this series – and with Lopez in charge as well as on camera, she can make sure to nail, and underscore, her most effusive outbursts. But if the dancing is as good as she says, where’s the harm?