Car rental in Fukuoka

Can anyone advise a good car rental company that I can pick up a car at Fukuoka airport. How much does it cost for a week. How much are road tolls. I plan to visit major cities and attractions in Kyushu around Christmas 2008 with my family of 4. Is is worth driving instead of catching trains / buses ? Are road conditions ok. Thanks.

Can anyone advise a good car rental company that I can pick up a car at Fukuoka airport.

Virtually all Japanese car rental companies have outlets at Fukuoka Airport:
http://www.japan-guide.com/e/e2024.html

Here is the cheapest service that I am available of:
http://www.japan-guide.com/ad/coocom2.html

How much does it cost for a week.

The smallest cars at the cheapest outlets start around 4000 yen per day. A standard car at a standard outlet will cost you more than 6000 yen per day.

How much are road tolls.

Only expressways cost tolls. About 20 yen per kilometer.

I plan to visit major cities and attractions in Kyushu around Christmas 2008 with my family of 4. Is is worth driving instead of catching trains / buses ?

Yes, if there are four of you, it can be economical to rent a car.

Are road conditions ok.

Yes.

We rented a Mazda through ToCoo at Fukuoka airport but soon found its GPS could not locate many sites, including the must visit ones in Beppu as well as some restaurants. We complained to ToCoo and they just made excuses. In the end we had to sort it out with Mazda directly. The local police suggested we try Toyota which has a branch right next to Mazda in Beppu and we inputted the 4 sites and restaurants which the Mazda GPS could not locate and the Toyota GPS got them all. So we switched to Toyota on the spot. Toyota costs more but the cars are much newer and because we were heading to many out of the way places in Kyushu, we just could not afford to be stuck at night in the middle of nowhere looking for our destination. We had no trouble through-out the rest of our 10 day trip with the Toyota.
For Christmas time, depending on where you are going in Kyushu, we may need snow tyres. We should call the tourist information centres as well as Toyota to find out more. Personally, I would say, costs aside, you would have a much much better holiday driving than otherwise, especially in Kyushu.