swerve drive is harder then you think do not rely on chains.::rtm::
1075 did a 2+2 swerve configuration for the last two years (for the 2010 FRC season we designed and built DSSwerve, AFAIK to date the ONLY FRC bot with invertable swerve drive)
Swerve is hard to do well. Our 2010 incarnation of swerve worked fairly well, but we had a driver with 4 years of FRC experience, and our 2010 DSSwerve was derived from our 2009 Swerve.
2010 DSSwerve suffered from throwing chains, bending swerve modules via side-loading when being pushed, and more. The worst part about building a swerve system is that the mechanical complexity of the system makes repairing failed parts significantly more difficult, and can often result in needing to disassemble large portions of the robot, depending on which part has failed.