Riverdance Show is a cultural phenomenon that defies criticism for the enthusiastic and leaves everyone else scratching their heads. The wonderfully talented cast, headed by the Riverdance Irish Dance Company, bewitchingly spins (and stomps) its Celtic folk choreography featuring numerous breathless solos by Michael Flatley (since departed) and Jean Butler. The mellifluous Riverdance Orchestra boasts Davy Spillane, who coaxes plaintive lamentations out of a peculiar instrument that resembles a bagpipe in a metal leg brace. For Enya fans, there is the sound-alike choral group Anuna, who casts a similarly New Age-style vocal spell. Also thrown into the mix are such disparate folk traditions as American gospel and Spanish flamenco. Though it's only 70 minutes long, Riverdance is repetitive by half. But judging from the ecstatic audience ovations and the continued foot-stomping during and after the curtain calls, too much is still not enough.