I am serious about Avast and Avira. I only "think" I would purchase Kaspersky or maybe Sunbelt Viper.
I like Avast because it is hassle free and has a boot time scanner. As far as Avira goes, it has a lot to do with how you set it up and manage it. I like Avira because it is hands on, very effective, and informative if you set it right.
I am using Avast 5 right now. How about you, Ross?
Windows XP Professional 2002 sp3 32bit
Aggressive AVIRA 10, MBAM, SAS, Sandbox
Everything that has been and everything that will be, exists, in some form, within and without, the known and unknown universe.