I was an administrator of a 99% Mac environment my last 10 years of productive work and the only, and I mean the only issues we ever had was with MS Office. I handled over 200 users / year and how each had a Mac and Never was there an issue with malware or virus'. NEVER! Now of course those up the chain provide a license for Norton but with or without Norton I NEVER saw any issues. The biggest problem with the computer was always how the user could find something to screw up. After Apple came out with OS 10 where folders had to be in there place then users could mess up the computer. All the OS's prior to OS 10, a user found it almost IMPOSSIBLE to mess up.

Go Slow
Sail Far
Stay Long