Well, see, you know what you're doing. ;)
Well, I dunno. I'd rather be lucky than good. :-)
In my world though, I hide everything behind really good firewalls (I dig PIX) and get pretty jealous of what I let through. I also strip off any executables (among others) from e-mail messages. I have for years. It's saved me a lot of grief waiting for AV providers to update files when a new pattern needs to be released.
I also have four (count 'em, 4) levels of antivirus protection from two different providers, at all levels... SMTP, Exchange, User, and NT Share... I wouldn't be so brave as to get cocky, but so far it has worked out pretty well. :-)