Longhorn = Windows Vista
With product names, my feeling is that anything new takes awhile to get used to, especially after using a codename for several years. It's hard to imagine a creative name for a new version of a product that people would love instantly (although I thought Xbox 360 was a good choice). I just remember how much some of us on the CLR hated the .NET name when it was first revealed! I wasn't sure about the "Windows Vista" name when I first heard it, but now I actually like it!