Are you dissatisfied with Microsoft's Vista? Have you, or are you considering, up/downgrading to Windows XP? Do you think Vista is Windows ME take 2?
I had already begun my move to Apple's OS X Leopard. I am very happy there so far. I am very pleasantly surprised at how little I miss Windows for my day to day computer use.
I have lost faith in Microsoft's ability to delivery software I want to run. Even excellent exceptions like Windows PowerShell, the C# language and the .net Framework [versions 1.1 & 2] are not enough to keep me a loyal Microsoft operating system user. An MS/DOS user since 2.11 and a Windows users since 3.0 on an 8086 (I did play with a even earlier version of Windows before there was any non-Microsoft Windows software), an early adapter of everything Microsoft for over a decade now, I have to confess the last time I got excited by Windows was in the final beta of Windows XP.
It may be all over for me and Microsoft now. Time will tell. I have lost faith that it will find its way back to me any time soon.