I don't know about you, but I have a little bit of the Leopard fever. And while you might be immune to all the wonders that Leopard has in store for us, Amazon shoppers seem to be as gaga over Apple's big cat as I am. Leopard is currently sitting at the number one and two spots on Amazon's Software Bestseller list (the Family Pack comes in second to the single license) due, in part, to Amazon's aggressive pricing on Leopard ($109 for the single OS license and $189 for the Family pack). The next highest OS on the list is Windows XP home edition which is at number 28 at the time of this writing (though to be fair, XP and Vista have both been out for awhile, so it makes sense that a brand new OS would garner more attention and buyers).
It is also interesting to note, in light of the new marketshare numbers, that Mac software has 6 of the top 10 spots on the list (Office 2004 is at 4, iLife '08 is 6th, .Mac is 7th, and Parallels is 10th) and that 10 of the top 20 spots are inhabited by Mac software.
Keep in mind these rankings are valid while I am writing this post, and might change given the nature of Amazon's Bestseller lists.