It turns out ars technica published an excellent article on the transitions Microsoft experienced during XP to Vista and Apple when the ditched OS9 for OSX.
Titled: From Win32 to Cocoa: a Windows user’s conversion to Mac OS X it comes off as a quite misleading almost fanboy-esq bitch fest at times but has some excellent history lessons and is a wonderful insight into a disillusioned Windows developers life.
XP was released in 2001. And that was basically it from Microsoft for the next five and a half years. Until Vista, Microsoft didn’t bother putting out a single new client OS. Meanwhile, Apple released Mac OS X 10.1, 10.2, 10.3 and 10.4. It continued to tidy up legacy features (deprecating QuickDraw, for example). It added new APIs like Core Audio and Core Image. It made sure that these APIs were of high quality—Core Audio offers extremely low latency, for example, and Core Image provides high performance accelerated image processing—and it consistently ate its own dog food. This produced high-quality, best-of-breed applications such as Final Cut Pro, Soundtrack Pro, and even Aperture (after an admittedly lackluster initial release) that leveraged these new technologies.