I've seen a lot of people on the forums complain about that it's mac pro or bust in terms of expandability and I was wondering for those who decide that they must have one, what makes it necessary for you and how have you used its unique features in the Mac line-up? For example, what use do you have for the PCIe slots? Why do you need so much storage? Are dual-displays not just a luxury? I thought it would be interesting to find out how the power users in this community make use of their machines.