You have to "read" comments not "hear" them to give them any credit. I suppose you heard them from friends or acquaintances?... So, what are they, experts or at least know them to have had wide experience with Avast that you should trust their comments?.
I have used Avast for 8 years without having a serious infection... and it's gotten even better since version 5-6, and I will not install any other antivirus. You can search for yourself with: "Top free antivirus programs", "best free antivirus programs" "Top 5 free antivirus programs" or similar searches, and you will find that Avast is listed as either Num 1 or 2 or at least 3rd... read the comments and see if you find anything negative in them.
The only time I ever had a serious virus infection was with AVG. And the only issues with Avast have been trojans but those are not all caught by antivirus software, that's why antimalwares are developed.
In any case, other free antivirus programs worth trying are AVG and Avira
Best Free Antivirus software 2014
http://www.techradar.com/news/software/applications/best-free-antivirus-9-reviewed-and-rated-1057786
18 Best Free Antivirus Programs for 2014
http://freebies.about.com/od/computerfreebies/tp/best-free-antivirus.htm