smallnetbuilder.com has an article (Build your own UTM with pfSense) showing what you can do with pfSense as Unified Threat Management appliance, esp. with regards to
Intrusion Detection and Prevention, Anti-Virus, Content Filtering, Anti-Spam and Traffic Control.
The concept of Unified Threat Management is straightforward: on the outer reaches of your network perimeter, you install an appliance that stops all possible threats to your network, an über firewall, as it were. The fact of the matter is that UTM hardware is expected to completely overtake separate network protection hardware.
pfSense can perform all these functions to some extent. To judge how well pfSense meets these UTM requirements, I’ve given a subjective grade to each set of UTM function groups. Once we’ve defined how these functions thwart threats, and how pfSense meets those challenges, we’ll upgrade Cerberus, and see how it performs as a UTM. more
The article concludes with:
With pfSense, this content is largely free – making pfSense, with all of its patchwork flaws, very compelling. The value proposition of pfSense is significant. It is free, open, and no expensive subscriptions are needed to protect your network. Free something is better than nothing.
Chris Buechler has also announced the availability of pfSense 2.0-RC1 (pfSense 2.0-RC1 now available):
Years and many thousands of hours in the making, pfSense 2.0 Release Candidate 1 is now available!
Check it out, test it, and leave feedback on the pfSense forums