None of this OS development has happened overnight. BeOS is 5 years old, the original BSD is more than 15 years and FreeBSD is close to 5 years. Yes folks, it does reach that far back. Compare these numbers to Windows 9x at less than five years, NT at slightly more and Windows 2000 just being born. Some of the instability of Microsoft operating systems is simply due to its youth, and some is due to the huge amount of new code in each new version.
Reliability takes time to develop.
Five nines amounts to 5.25 minutes of downtime a year. This is a significant accomplishment, requiring redundant hardware and specific software. Don't expect your PCs to ever reach this level.