BMW Power:
I have been thinking about your project and this thread. If I were to summarize the thoughts I would do so this way.
As people indicate and I reluctantly admit

concrete is a more durable, longer lasting, hard surface for your driveway. However this comes at both a considerable price for the material and an increasing need to have a perfectly prepared surface to avoid problems down the road because it is not flexible. Asphalt is more flexible but also less durable and more prone to piercing and punctures.
One of the compelling reasons you described for doing the driveway in concrete is because you can do a piece at a time yourself, therefore making the project more affordable. However further input in the thread indicates that this both makes the work a bit more complicated and the potential for problems increases doing it in small quantities versus doing it as 1 pour. In addition the cost of concrete in smaller quantities seems to be accompanied with higher costs, in particular delivery charges. I am assuming you do not have significant experience doing this kind of concrete work (I know I don't) and I think that added onto everything else spells the potential for expensive disappointment. Because of the nature of concrete you cannot "redo it" without tearing it up and repurchasing the product.
Have you considered doing concrete pavers instead?
The funniest thing of all is that your post is about the cost of concrete and a bunch of us, me included, can't help but express our opinion about the project in general. I love this board.
Cheers!
Jim