I have been running Avast (the free version) for about 6 months, ever since I got several virus and trojans and had to reload software. Well three days ago Avast warns me that i have a trojan. I go and look, sure enough. Every time I put it in the chest it comes back... crap. Ran Avast at boot up, found some more trojans and virus's. Ran a online scan from PandaScan. . killed some but missed others. Got ****** and ran CCleaner (empties all temp files, all cache folders, cookies and bunches of other crap). Then I ran scans again... . all gone except for the trojan. Went online to Avast, and found there forums. Posted up my problem. Within 24 hrs someone had helped me get rid of all traces of the trojan (with the help of two programs that do some magical stuff) and told me how it got into the system..... (an old version of Java he suspected). New java installed and bugs are gone. Avast may not have caught it coming in but the help on there forums sold me. I may even buy the retail version.
That being said I have run AVG's 30 day trial and it works good.