I have used it, it was great. It is a special motherboard made just for that machine and they are only take intel chips from what I have seen.
without cutting some major holes in it and using a external power supply you wont be able to get a diffrent board in it.
my only complaint about the unit was that it has no PCI
Edit: also they run off of a external power brick that puts out 19volts at 3.2 amps