Taken out of context apparently. Keep reading:

http://windowsvistablog.com/blogs/windowsvista/archive/2006/12/12/title.aspx

"As part of one of Microsoft's on-going lawsuits, a piece of email that I sent to Steve Ballmer and Bill Gates recently became public.  It was a rant encouraging a change to the way we were building Windows at the time.  In the email, I made a comment for effect about buying a Mac if I was not working at Microsoft.  Taken out of context, this comment could be confusing.  Let me set the record straight:

• This email is nearly 3 years old, and I was being purposefully dramatic in order to drive home a point.  The point being that we needed to change and change quickly.  We did:  We changed dramatically the development process that was being used and we reset the Windows Vista development project in mid-2004, essentially starting over.
• 2-and-½ years later, Windows Vista has turned into a phenomenal product, better than any other OS we've ever built and far, far better than any other software available today, in my opinion.  It's going to be available to customers on Jan 30, and I suggest everyone go out and get it as soon as you can.  It's that good.

The spirit of being self-critical continues to flourish at Microsoft.  Within Microsoft everyone considers it their duty to always put their convictions and our product quality ahead of everything else.  That was the intent of my mail to Bill and Steve, and I consider it a great example of how this company can focus and do what's right for customers."