I'm considering building a robot similar to Taurus 2. I'm wondering about some of the disadvantages of holonomic robots. It looks like using a holonomic system will create a bit more computational overhead, but not too much. Localization will be very important to me - will a setup such as Taurus 2's significantly degrade my ability to do accurate dead reckoning? Taurus 2 uses 8 identical servos. If I should upgrade my 4 wheel motors later, I could probably get away with using weaker motors for the 4 'swivel' motors, right?
Lastly, I'm making a 4-wheeled robot. If I decide to just do differential drive, how would I go about attaching my 2 motorless wheels?