A truly good extra virgin olive oil has vitality and character; it is alive – much like a good wine. It bears the aromas of the fresh vegetal world. In your mouth, the flavors blossom and then linger. In contrast, poor olive oils are a boring, inert experience – no smell, little to no flavor, and often a distinctly oily texture. If they are old, there may even be a slight but persistent rancid smell and flavor, like old peanuts or old oil paints.
We have a great page on the Little Angel website all about how to taste olive oil.