I agree with 53119's assessment of Oakley. I have a pair of Flak Jackets. My first "good" pair of sunglasses. The optics and comfort/fit is absolutely amazing. once I put them on I don't want to take them off. I feel a little too "terminator" while dropping off my daughter at pre-school, but they aren't really THAT extreme. Then again, I've also got a pair of $17 Sette glasses from Price Point in my camelback...rattling around loose, no case, who cares. I lost a pair last summer, bought another one.
So, in summary I guess I would say it really depends on your personal situation. The high end Oakley (and comparable brands) stuff is nice. You will pay for it, but you will know why. And you will do your best to take really good care of it. If all you want is something to stop a rock from hitting your eyeball, get a $17 pair of Sette w/multiple lenses and rock & roll.