I have severals tweaks with group policy that combined with a decent a/v malware is reduced to a small chance.  Now that this is now true as soon as they open up the partner branding I have one client that uses avg, another that uses Kaspersky(which is currently turned off due to it causing issues), and a third using trend.  All of these are going to be transitioning to MS Security essentials.  I have used it extensively and it works very well without the network interferences of most of the other “security suites”.

Announcing: Microsoft Security Essentials available FREE to Small Businesses in October! – Microsoft Partner SMB Community Blog – By Eric Ligman – Site Home – MSDN Blogs.