Fish oil is a fairly common supplement in the fitness world, up there with protein powders and creatine. But similar to those other two, the effects are slight and not really detectable day-to-day.
Fish oils are being studied constantly, and at best they get a marginal stamp of approval. I don't think anyone (beyond supplement sales folks) are going to say they're absolutely necessary for a long and healthy life, but I also don't think anyone can just dismiss studies that end up with some rather blunt language:
The results of prospective cohort studies indicate that consuming fish
or fish oil containing the n-3 fatty acids eicosapentaenoic acid (EPA)
and docosahexaenoic acid (DHA) is associated with decreased
Fish oil falls into the category (for me) of car oil changes. You're not going to feel any differences after an oil and filter change, but in the long run you're delaying and/or minimizing other problems.
It's definitely something to keep watching the news for; it's something that's getting studied frequently so today's data will be only part of the story next year.