I have tried before to make a Rocker-Bogie robot, similar to NASA’s Mars rovers. But with the NXT I always had a shortage of structural parts, leading to incomplete and unstable constructions.
With the EV3 it works surprisingly well, and I was able to power all the wheels with two motors, and leave enough parts to make a robotic arm.
It looks lovely, and the principle works, but the actual capabilities are slightly disappointing as the torque is very limited. Climbing any large obstacles pushes the bogie off the ground and rattles some of the many gears.