Everyone has an opinion on AV programs. Anecdotes aren't really useful, however. I show our customers the latest results from AV-Test.org and AV-Comparitives.org so they can choose based on test comparisons. I have had hundreds of customers that claim they had no problems until "yesterday". Manually scanning the pulled hard drive usually shows malware files from as long as a couple of years ago. They just happened to pick up a particularly nasty one the day before, and then noticed pop-ups, extreme slowness, or other issues. We currently recommend Kaspersky for business use, as it isn't as bloated as Trend Micro or as buggy as Bitdefender. All three are highly rated currently. Others fall short on the test results. Among the free choices Avira is a top performer. 360 Total Security is currently even better, as long as you manually select the add-on Avira and Bitdefender engines. People in general tend to recommend what they use no matter how good it really is in comparison to the competition.