Spike, good points. I just did a similar comparison between the CTS and the LT over in the V6 forum. You've got to hammer out the multiplication, Final Drive * each gear for overall flywheel to rear axle ratio. But if they're close, even in the 6L80's favor, remember the parasitic loss from the front pump and added weight of the auto versus manual. (I don't think it's as much as that comaprison used to be, in fact I just checked it on chevy's website and they have the auto listed as only 53 lbs heavier, but it needs to be factored in since we're splitting hairs
) Yes, the shifts on the auto are going to way faster, you're right, but the added weight, parasitic front pump losses and decreased horsepower of the L99 might tip the scales in favor of the Manual. Sounds like the engineers have already confirmed this though.