Eddie M, I can't agree with this. 99% of the problems I see at this time are with Spyware, Malware and the like. OK ports are scanned and occasionally Windows attacked however infections of outgoing traffic seem far more prevalent these days. A good software firewall would have stop most of this as well as giving the user a clue that something was amis. I also find that the router based firewalls are far too complex for the casual user to configure correctly, some of the users I've dealt with have suggested that the router said it had a firewall, so they were not worried. The fact that out of the box, it afforded little or no protection was of no consequence.
Unfortunately, a software firewall does not protect against the installation of malware, it only serves to mask its effects. In fact, but telling your software firewall to block traffic and then not to bother you again is folly, as you have then effectively locked the malware inside.
They also prove difficult to manage in a network situation because they exist in the wrong place. A firewall should be situated between networks and not within them. Also, most spyware is self inflicted by downloading other untrustworthy or "attractive" software containing a payload.