Over the last 12 years or so I've used all free ones, AVG, Avast, and Avira mostly. Gave Kaspersky a short try one time, it seemed a bit top heavy. The others have had their good days, but when they start to try taking completely over I generally wind up switching. I guess my next test will probably go with the MS, and see how well it works. It did rate very poorly in the "Protection" area of these tests though