Vista Signature Edition?

I was reading some articles over at Keznews.com and I stumbled across this article "Amazon features signature edition Vista upgrade". So, me being inquisitive...had to go and verify this...sure enough...here it is:



So far...the only difference I have been able to find between this and the standard version is Bill's signature. There is nothing on Microsoft's Vista Editions site that even mentions the signature edition...so I figure my assumptions are right that you get the penmanship of Bill himself on this limited release.