thanks for pointing me to the Dock preferences 
I tried and found the black triangle blinks instead,
with the same interval as the bounce
but I think the bounce/blink is not the cause for the slow launch.
just check with the Activity Monitor during apps loading.
Most of the cpu time etc. are spent by the Apps,
not the Dock displaying bounce.
Eliminating bouncing animation won't do much good for launch time
These eye-candies (bouncing, drop shadows, transparent menus)
do not cost much with the powerful Quartz Extreme...
I tried and found the black triangle blinks instead,
with the same interval as the bounce
but I think the bounce/blink is not the cause for the slow launch.
just check with the Activity Monitor during apps loading.
Most of the cpu time etc. are spent by the Apps,
not the Dock displaying bounce.
Eliminating bouncing animation won't do much good for launch time
These eye-candies (bouncing, drop shadows, transparent menus)
do not cost much with the powerful Quartz Extreme...