If I didn't know it was installed, I wouldn't know. I'm not expecting any viruses, but so far it has not messed up my Mac in the least.
The only downside is if you have it regularly scanning you hard drive, the 'Norton Missed Tasks' background app eats up CPU cycles, so I turned that feature off and only have it scan my downloads folder. Just for fun I saved one of those zip attachments that I got on some junk mail that's supposed to be from UPS, and it detected the virus right away and removed it from the file. But I have been freelancing at Sony Music, and they use it, so I figured what the heck I'll give it a whirl. I haven't used any Norton products, or antivirus software for that matter, in a very long time (since the dawn of OS X). Well I got this for free as part of the whole Norton Security package from Comcast/Xfinity.
