AV test.org one of the well known antivirus testers tested 23 antivirus programs in a windows xp (32 bit) computer.avast! free antivirus done well and got 15 points which is quite high and beats most of the competition out there. http://www.av-test.org/en/tests/home-user/julaug-2012/. Congrats avast! 
I can’t see how a product can be given 6 out of 6 for usability yet an abysmal 2 out of 6 for protection. That just doesn’t make sense, who cares how easy it is to use if it isn’t protecting you; ah I know makes it easier to get infected.
For a security based test I don’t know why usability even comes into it, when the greatest majority of users would be using default settings on their AV.
Same thinking over here. 