I once used Avira Free Antivirus (AFA below) a few years ago. The program is ugly and stupid. But now in 2015 things seems to get better, the program looks cleverer than it was. I tried it a few days but finally uninstalled it.
The Avira Launcher is really annoying, you must open it first, then open AFA. It shows some other Avira products icon with grey color, it drops a hint that "you have not install our other products yet". I really don't need them, but I must bear it every time I want to config the antivirus, this is not friendly, really.
The antivirus keeps remind me Windows Firewall is not active. Well. But I don't like Windows Firewall, it just give a few more windows waiting for my permission. AFA can active my Windows Firewall automatically if I let it go. For some unknown reason it would shut down again at next system reboot, then AFA would tell me I'm not under full protection again... But why are they like Windows Firewall so much? It's a good chance to advertise their internet secure product I think, and it would not get people annoying like that Avira Launcher.
The real reason makes me to uninstall it is it bugs. Today I unplugged my keyboard and plugged it again while system was working, pressed many random keys while fixing my keyboard, and some other things I can't recall clearly. At next reboot my system became extremely slow, and it reproduced with one more reboot. I once wanted to reinstall my system but just before that I tried uninstalling AFA. Oh yes everything back to normal!
== About other antivirus I tried ==
avast Free Antivirus:
I used avast for the longest time. Its interface changes frequently, and not always be better than the previous. Quarantine became a little concealed from version 2014. The mainly problem I find recently is it slowed down my Kega Fusion performance after a long time system running without reboot. I can't always run my system and Kega Fusion such a long time to reproduce it so I can't even report. You must add your daily use apps to exclusions or else lags when the app starts (this really sucks IMO).
Troubles me after installing, wrong system language detected and hard to fix, and uninstalling troubles too. I searched on Internet, the problem found very early (2011?) and now it still remains. It also so much likes WIndows Firewall, and Windows Update, but can these products splitted?
AVG Anti-Virus Free Edition:
Similar to Avast and does not look bad, it can add stuff to exceptions at report window at first but not later. Maybe what detected by that "Resident Sheild" can't be add to exceptions in the report window. Anyway, this confuses me. If you ignore it the program will keep alarms... Another problem, my internet connection had some problem during its installing, and the installation stalls. After a few minutes it still stalls. I find it impossible to roll back the installation, no close button, had to end the process manually. Ouch! Don't know how many trash left on my HDD... Another problem, the Chinese page is highly incomplete, it could misleading people, and the register access in the program is led to the local page, that means, Chinese version of antivirus will lead you to Chinese page, the problem is... Chinese page is incomplete, there is no way to register! They should not add Chinese page at all if they are not fully prepared IMO.
Really hope all the antivirus stop their stupidness.