Vista and IPv6

I know C|Net is not so popular here... but this article was interesting:

Microsoft's launch of Windows Vista could slow down or stall traffic on the Net, said Paul Mockapetris, who is widely credited with inventing the Internet's Domain Name System (DNS). Mockapetris believes Vista's introduction will cause a surge in DNS traffic because the operating system supports two versions of the Internet Protocol, a technology standard used to send information over computer networks.

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I had forgotten that XP does not support IPv6. For that matter, I'd turned it off and stopped thinking about it long ago on my macs as well. Although I guess when I upgraded to Tiger and when I got my iMac, I may have gone back to auto IPv6.

I'm certainly aware that it will eventually be necessary.

Do most people have it turned on or off (for performance enhancement because it is not necessary)?