Aaron-
There are some great attributes to center drive designs. The two biggest imho are simplicity and maneuverability. If you want to be able to spin in place it is a great system because you have very little scrubbing. Because you only have 2 drive wheels it is simple and lightweight.
But.... like the others have said, it won't work if you are going up ramps or over obstacles. You get high-centered. If you are in a pushing/pulling contest you HAVE to make sure you get weight on the drive wheels and NOT on the casters. Casters will kill ya if you don't watch out.
Every year our team has done center drive (1997, 1998, 2000), we have made it to the national semifinals, so it *must* be good....
) BTW, in 2000 our center drive was "enhanced" with shift-on-the-fly rear-wheel-drive wheels to get over the ramp, so you can't count that one as simple.
Ken
P.S. The reason we are on here so long before the season is we are, uh, geeks. And I mean that in the most complimentary way!