I learned long ago that olive oil had a bitter aftertaste if used in cooking. I've found that I don't notice if I do what I always do: load up on the flavors and spices. But, I have noticed it when I use it to fry eggs. It's subtle, and I wouldn't call it bitter, but it's there. I still prefer to use a neutral oil for frying, and I have plenty of it, so I can keep on doing that, and reserve olive oil for other purposes.
I don't like using OO for frying eggs, especially EVOO. The taste of the oil is too strong for the subtle flavor of the eggs. I only use butter for eggs. They cook so fast, and I use a medium/low temperature, so burning the butter is not an issue with my eggs.
CD