I'll tell you something else. It might be simplistic and rendered useless *once* you're infected but, I think having a registry key monitor can add nice layer of security against malicious programs, especially trojans (as I've noticed over time, alot of them deposit new values in the registry so they can start on bootup, etc.). SoBig.F is no stranger to this as it also deposits its own values into the registry keys. It may not be proactive (registry key monitors) but I think it's a great idea to have in the long run.
In case you're interested in TCMonitor, check out MooSoft
Check under The Cleaner (even though The Cleaner is a 30 day trial, I believe TCMonitor is free with the bundle).