I'm still a very happy user of
NOD32. Their name is not that wide know as McAfee, Norton, AVG and such, but they are really good. Before it i always used Norton Antivirus, but it became slower and slower in their new versions. NOD32 is very reliable and won many awards. Their interface is very clean, it does what it's supposed to do: scanning virusses
. I have it configured to silent mode, you just forget you have a virusscanner on your PC until it found a virus it or for whatever reason can't update itself
.
I have used AntiVir for a short while too on a PC from somebody else. But my experience wasn't great. Can't say what the bad point was, it just didn't feel right. Couldn't get used to their interface and slpash screen showing at startup either
.
Never used AVG, have heard many bad stories about it, but on the other site see many happy users aswell.
EDIT:
If you want to know how reliable diffrent anrivirus programs are, visit
Virus Bulletin. They do good test (known as VB100) on all well known antivirus programs and show how reliable and fast they are.
Results from VB100 test May 2005 (click to see bigger version). See the full article, including how the test was done
here (PDF document).
Everytime when an antivirus program has scanned and stopped 100% of the viruses used in Virus Bulletin's test, the program is awarded a VB100 award.
NOD32, which i use is the only program which was rewared the VB100 award on
every test Virus Bulletin did since May 1998
. Also they have always been one of the fastest virus scanners around (see rest results)
.