From a visual standpoint, this episode is a marvel (especially for a character based story). The two Rikers share scenes as if there are two Jonathan Frakes working together on set, and perhaps even better, we get to see Dr. Crusher and Counselor Troi in sexy futuristic nightclub clothes (if only briefly). But from a story standpoint, the plot is a lead balloon, doomed from the start to never get off the ground.
Will Riker is the Enterprise's everyman. The character works best when he serves as the audience surrogate in bizarre circumstances ("Future Imperfect," "Schisms", "Frame of Mind".) And while it might seem like the sci fi idea of a character doubling himself falls into this category, the truth is that it plays out as something more ordinary -- like a story about a pair of bickering brothers. Had the idea been used in the first few seasons of the show, the result would have probably been worse. Fortunately, by the sixth season the show is able to turn the lackluster idea into a watchable episode (thanks largely to a great directorial debut from LeVar Burton and strong performances all around from the actors -- especially from Frakes, Sirtis, and the other Frakes.) Of note, real life astronaut Dr. Mae Jemison (the first black woman in space) has a cameo as the transporter operator.