I found the results of a recent study quite surprising:
In the first six months of the Vista life cycle, Microsoft has released four major security bulletins that address 12 total vulnerabilities affecting Windows Vista.
In comparison, the most popular Linux distribution, Red Hat Enterprise Linux 4 Workstation, was swamped with 129 publicly disclosed bugs in shipping components, 40 of them "High Severity."
Full story:
http://www.eweek.com/article2/0,1895...LNAV062207FEA1