The New York Times provides preliminary numbers for the fully assembled PowerMac G5 Cluster which Virginia Tech assembled this month.
The preliminary numbers rank the G5 Cluster as the 4th in the world in performance with 7.41 trillion operations per second (TFlops) . Official results will not be reported until November, and Tech reports that they are "still finalizing their results and that the final speed number might be significantly higher."
The relative cost of the entire assembly is significantly less then previous solutions.
The Top 5 Supercomputers as of June 2003 are listed here. The #1 computer comes in at 35.86 TFlops, #2 at 13.88 TFlops, #3 at 7.634 TFlops, #4 at 7.304 TFlops, #5 at 7.304 TFlops. At 7.41 TFlops, the PowerMac G5 Cluster should slip into 4th position... and is not very far from the #3 spot with these preliminary numbers.