Use your macbook/macbook pro in the car with car adapter?

My local CompUSA, which is currently shutting its doors along with the rest of them, has a bunch of the Apple car adapters for MBs and MBAs in their discount bin. They are new in the wrapper. If you have one nearby, check it out.

If you have to drive more then 4/5 hours, use an adapter, but if you have to drive less, just use it on battery-power. When you arrive at (work/home/school) plug it in an outlet.