This eWeek article provides some interesting details that weren't mentioned at MacWorld regarding the new G4 Towers. Of note, it seems there have been slight changes to the motherboard:
the replacement of certain bridge chips should boost top throughput along the PCI bus to a maximum of 215M bps, almost twice the previous rate, representatives said.
As well, "the top-of-the-line model, which sports dual, 800MHz processors, will see a boost in actual throughput thanks to more efficient data flow between the twin chips' L3 caches (each of which are 2MB)"
