First tests of new Nehalem MacPro through Geekbench are very encouraging : the 8 cores/2,92 Ghz (high end model) is globally 23 times faster than a single 1,25 Ghz G4 (18 times faster on integers, 32 times faster on floating point calculations, 10 times faster for memory access, and offers a 14 times larger bandwidth).
However, there has been globally few progress since G5s (were unveiled close to 6 years ago).
Cjed Audio 