We are driving from MI too. It takes us 19-19.5 hours and of course we do this over 2 days. We are actually taking a break in our trip and driving 14 hours to Alabama to visit hubbys relatives for a couple of days and then finishing the 8-10 hour treck to Disney.
I am dreading the drive only because we just checked out a week ago today and took that 2 day drive back and I have to do it again in less than 6 weeks. But it is still cheaper than flying. I know we could get there in 2.5 hours with flying and that is definatly worth something but it would have run us around $950 to fly and it cost us $365 in gas. This may be a little high due to the fact that almost the entire way down it was 2.99 everywhere because of Rita and also because we made a stop in Ohio and did a couple of things.
I am dreading the drive only because we just checked out a week ago today and took that 2 day drive back and I have to do it again in less than 6 weeks. But it is still cheaper than flying. I know we could get there in 2.5 hours with flying and that is definatly worth something but it would have run us around $950 to fly and it cost us $365 in gas. This may be a little high due to the fact that almost the entire way down it was 2.99 everywhere because of Rita and also because we made a stop in Ohio and did a couple of things.
It helps that we are in South Florida, and under 220 miles south of there. We cannot wait. Aviva keeps asking if after we sleep are we going to see Mickey!
Well, have a great time and I can't wait to hear about your first trip! 
We will also be driving to WDW in December. We will leave on Friday the 16th after work - we are coming from Conway SC (about thirty minutes outside of Myrtle Beach) It will take us about 8.5 to 9 Hours depending on our stops and road construction. We will only drive about half way and stop and spend the night then get up fresh the next day and drive on in. I would rather fly but my DH would rather drive, so I let him do all the driving (I hate to drive even at Home!)
. Often on the way down we will start after work the evening before check-in, stop somewhere in mid-Georgia, then get up early to arrive at WDW between noon and 2:00 pm. The drive home is generally an all day forced march (of sorts) to get home of about 10 or 11 hours.
Newnan is a cool little town, stopped by there once on the way to visit my sister in Atlanta. Hope you guys have a great trip, we're not far behind you, Dec. 8th for us!