51 seconds to burn and 512 seconds to verify the flash does seem very long. That sounds like it might be a result of what kg4wsv suggested: that the avrispmkii is configured with a slow clock period. The delay at startup though, is because (assuming it's the same as it was in my case) avrdude tries to sync with the avrispmkii 33 times, and each one has a long timeout.
OK, but is there any way to put the "sck 10" into a command line option for a script?
aaaannnddddd .... to add some more fuel for pondering ... I just strated up to burn some chips and did ONE THING different ... instead of plugging the USB cable into the side of he MacBookPro I plugged it into a spare port on my Belkin 7 port USB hub ... and, voila, no 5 minute wait, it immediately started doing its thing. Total time start to finish was just under 10 minutes (essentially just under 1 min for burn, just over 8 min for verify, and the rest for locks and fuses) and quite repeatable I am on my fifth chip .... how does this fit in with your theories?
... wheee ... are we having fun yet? -grin- this is making me sweat, but I am an old dog learning new tricks!
cheers ... BBR