If you're gonna build your own, take a look at ours and the thread that developed from it:
here.
Our alumni mentor also further refined our design to work with the VEX Versachasis (which can be found
here)
Bomb Squad has some nice ones that they are trained to use to the fullest.
We partially used swerve in 2012, and it hasn't returned to the robot since (and I don't think it will return anytime soon).