Kudos to Apple for releasing a security update that will halt recent malware attacks. I guess sooner or later this was bound to happen as Macs are gaining market share and becoming a viable target for malware developers. But I have yet to see any Mac infected compared to the regularity that I see infected PCs.
This particular threat is a trojan, which is technically not a virus, but it's still malware that nobody wants on their computers.
Until I actually see a Mac infected, I wouldn't strongly recommend for Mac users to immediately go out and buy security software, but if you're a Comcast subscriber, you can get Norton Security for your Mac (already included in your subscription) and Verizon subscribers can get Verizon's Internet Security Suite (from McAfee) that also supports Macs.