I eat a lot of fish maybe because the ocean (and fish piers/markets) are only a couple miles away. You can't beat the taste of fish caught that day even though fishes like salmon and halibut are imported from the Pacific. Even with the local availability of fish, it is more expensive than poultry and meats ($7.99 - $15.99/pound for fishes). Canned fishes (tuna, sardines/herring, salmon) are cheap though so that helps average the costs down I guess.
I think fish is very healthy and I try to stick with sustainable fishes and avoid farmed-fish. I don't have it every day though as mercury is a concern and I do believe that it is best to have a variety of proteins (poultry, beef, bison, ostrich, pork, lamb, eggs, etc.) in addition to fish/seafood to get a wide variety of nutrients.