I take it too, I take fish oil and also flax seed oil in huge quantities. I take about 10 grams of fish oil a day and then just add the flax seeds and flax oil to my cereal, salads etc.
It makes a huge difference, but I find for me anyways, it needs to be in really high amounts, I mean higher than a normal person would need.
Just make sure you get a really high quality brand of fish oil, one that is guaranteed to have any heavy metals (ie mercury) completely eliminated. I take Carlson's Fish Oil, that is one my doctor recommended and it costs a little bit more, but quality is way more important than price or quantity!
HTH!
Edited to add: The only side effect for me was just that I broke out in a few pimples at first while my body adjusted to the extra oils in my system, but once my body got used to it, the pimples went away and never came back. 