Yes, 3 nights in Key West is worth it, and it's the perfect amount of time to explore the city's main attractions while taking in the iconic Key West vibes.  With 3 nights in Key West, you'll have enough time to explore Duval Street and its trendy bars, take a snorkeling trip to the stunning coral reefs, partake in the Mallory Square sunset celebration, check out some of the island's historic sightseeing spots such as Ernest Hemingway Home & Museum, and Truman Little White House, and even go on one of the many sunset cruises Key West has to offer.   Plus, 3 days allow you to go on an epic Miami to Key West road trip and explore Key Largo and the other keys along the way.