Is Delta Skymiles Worth It For Me? More mileage out of my skymiles

I've been a Delta Skymiles member for over a year now, and also signed up for their E-Rewards program that's similar to some of the cashback sites like Cashbaq and Ebates, and I currently have 18,000 miles sitting my account waiting to be redeemed for something. How much does 18,000 miles translate to in dollars and cents? Can I get a plane ticket with it?

Delta's perspective
Well if I could sell my miles back to Delta, at the $0.028/mile rate they charge me for buying miles, my 18,000 miles would be worth a handsome sum of $504. Delta is having a "Buy Miles 50% Bonus" right now that makes it $0.019/mile, not that that affects anything since it's not possible to sell miles to Delta :)

Plane ticket worthiness?
According to the Delta Award Mileage Chart my 18,000 miles could get me a round trip flight to anywhere in the US. I might even make it to the Caribbean! Or so I thought. Their