I always thought that an interesting thing about Vista was that although it was widely seen as a horrible failure it wasn't actually highly buggy. It had horrible problems with performance and hardware compatibility, but the software itself didn't seem to contain glaring issues - at least if you calibrated your expectations to the perception of its quality by the market and end users.

On the other hand, Apple always nails the user experience - a release like Vista just wouldn't get out the door. But they let other horrendous quality problems through that would and should be caught by better process.

So it sort of illustrates two fairly orthogonal axes of quality and how different companies excel in different directions along those axes.