My $0.02 comes as a link to "Real Good Food" which has a tutorial on olive oils and, of course a link to buy theirs. That being said, I am most impressed with the Don Alfonso. It shows fruit and pepper and bitter. A terrific olive oil.
What I have learned most is to think of olive oil the way I think of wine. By country and by region within country. And if you ever see a bottle of Quintarelli Olive Oil from the wine maker of the Veneto BUY IT.
The price will gag you but you will be rewarded 10 fold in flavour.
I remain deeply influenced by the family I lived with in Sesto Fiorentina. Treat olive oil as you would salt and pepper, use it as a garnish or an accent more than an indredient was the message.