We wanted to do a differential on ours, but alas we're trying so many new things this year we wanted to have a solid backup plan of just "driving around". It would be terrible for all of our new achievements to fail just because we made a mistake in our differential design. For this year, we're sticking with something that reliably works for us, and that's tank drive -- but with 2 omnis (possibly 4 if my CoM calculations were off
).
There's always the offseason though.