...this Broadway summer filler's main challenge is to inject variation into an entertainment built entirely around a single sultry dance tradition, defined by its heightened sense of melodramatic sizzle. But creator-director Luis Bravo's worldwide hit addresses the fatigue issue by steadily cranking up the degree of difficulty in the routines as the marathon progresses....Smirnoff and Chmerkovskiy are about as authentically Argentinean as Tango & Cash, but who cares? The crowd is mad for them, and it's easy to see why. They're tall, sinuous and sexy, delivering polished showmanship with effortless charisma. The four routines that feature the duo are among the highlights