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I just opened up 20 Finder windows to try this out and I did not have any lag at all. It operates at the same speed as it normally would.

I also have a MBP 2.2 with 2 gigs ram.
 
I just opened up 20 Finder windows to try this out and I did not have any lag at all. It operates at the same speed as it normally would.

I also have a MBP 2.2 with 2 gigs ram.

all windows are full screen size?
do you have Leopard?
 
I just tried it out again, and it turns out that there is some lag when you have 20 finder windows open full screen. I think the reason for this is that the CPU or GPU is deciding how to render the scaled down windows. The actual animation isn't too laggy.
 
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