I had Avira on my PC for 2 weeks (in combination with ZoneAlarm Pro firewall) in-between the expiration of BitDefender 2008 and the arrival of the 2009 version.
In that week I had the 'good fortune' of running into a Vundo virus, plus a whole horde of troyans which came in thru the back door...
BitDefender 2009 was the only one, by the way, that could get rid of the Vundo, as it's a tough little bastard. It's also the only A-V (for the moment) that runs without hassles on the new Windows 7 OS...
JJ