I just pre-ordered Mac OS X 10.6 from the Apple Store. Looking forward to Friday!
Not only does Snow Leopard not require the entry of any serial numbers, but the standard version of Snow Leopard is a bootable “full install” disc that doesn’t actually check for the presence of Leopard in order to install. This also means that if, at a later time, you want to wipe your hard drive and reinstall Snow Leopard, you won’t have to first install Leopard and then run a separate Snow Leopard upgrade on top of it.
That’s a relief.