Perfect? Probably not, but it's still the OS I'm going to recommend to my mom.
If you look at the numbers for OS X as opposed to Windows XP, OS X has 1,544 vulnerabilities in 153 advisories (~10.1 vulns/advisory) and Windows has 472 vulnerabilities in 358 advisories (~1.31 vulns/advisory).
Unless you have a good reason to believe that bugs in Windows are nearly eight times "more unique" than bugs in OS X, please don't compare advisories.
I don't want to point fingers at Chicken Little, because I agree with the thesis; Apple needs to be more serious about OS X security.
Okay, beside the snark it is true, Apple should maintain security bugs better and "File Quarantine" looks to me rather rudimentary: http://support.apple.com/kb/HT3662
But as long as the "Trojan Botnets" he mentions are simple PHP scripts which are distributed years ago by pirating Photoshop and are simply killed by deleting the file and a reboot I personally stay feeling pretty secure.