I was looking at the tech specs for the Playstation3 and saw that its CPU is a 3.2GHz PowerPC. If both the PS3 and the PowerMac G5 use similar PowerPC chips, why hasn't there been a speed jump for the G5? Look at the link below to see what I mean.
The PS3 will use a variant of the PowerPC architecture called the "Cell" chip, produced by IBM for Sony. As yet, these are not being manufactured but will be ready in time for the launch of the PS3.
Apple looked at adopting the Cell chip as an option (as Steve Jobs stated in the last keynote) but decided against it - I suspect this was because they felt that with the largest market for the chip being a console, there wouldn't be as much pressure on IBM to advance hte architecture quickly.