Oh, on topic, as to what Fett101 said. Apple didn't play with the numbers, the author of the article did. As far as I know Apple never made similar claims.
Oh ya, lets see those dells outperform the G5 in a cluster. RISC archtecture is famous for clustering, NASA uses G4 clusters. They are way faster than teh x86 variety.
YDL recently sond the US Navy a gigantic linux based G4 supercluster.