The slow machines are a G4 MacBook and a G5 iMac, both running OSX, 10.4.

One of the slow tasks finally validated. The wingman took 20 hours and finished on 12/12; my copy was done on the G4, which took just under 36 hours, and also finished on 12/12. Both were sent on 12/9. So slow machines do at least sometimes get matched and finish at roughly the same time. Probably Sekerob is right, they always get matched eventually, it is just hard for me to detect. There remain one task each that my G4 (sent 12/7) and G5 (sent 12/6) Macs finished on 12/9 that are still "waiting to be sent" to a wingman, and one G4 task sent 12/4 and completed 12/7 where the wingman is "in progress", so the matched queues apparently are not strictly FIFO by send or return date for these slow machines. Interesting...

My faster Intel Macs are getting matched to even faster machines, and both reply within 24 hours of one another. The only exception has been one "no response": the task was immediately sent to another fast machine that responded within a few hours.