I used to run spybot with no problems. Found it caught some things that adaware did not.
Don't have either now with ESET smart security (from chillisoft) although I do think some things sneak through their security too. Not perhaps viruses, but I do find miscellaneous ads appearing after I visit sites. For instance, I'm getting a lot of pop-up ads from a site that allows them, for Chevrolet Cruze's and have only been getting these since I looked at one on Sella. Suggests tracking cookies, which spybot and ad aware used to catch.
Did you know, that what you thought I said, was not what I meant :S
We used to use all the freebies (ad aware/spybot etc) but got a trial run of Norton with the new computer. Seemed very effective so we paid to keep it. I doubt it gets everything but it cleans out most tracking cookies and has alerted me to viruses trying to enter as well. Worth the money in my book - I got sick of having to constantly clean out the rubbish manually. In saying that I still check every couple of months to make sure it is doing the job right!
Hoping to get out of the city while I am still young enough to make the land productive.