It's a very subtle flavor and only worth getting at a top quality sushi place, or seaside if that's an option. Fresh out of the water is obviously best but even the best sushi place will have at least day old. Any older or frozen and the taste is really off putting.
I find almost all frozen seafood to be disgusting. I can deal with frozen shrimp. Everything else needs to be fresh, and raw or lightly cooked. I could eat raw fish and shellfish all day, every day.