For the 90 percent of Windows users not running a personal firewall, the new and improved firewall in SP2 may be better than nothing, but it's just not good enough. I, for one, would never rely on it.
As I've reported before, the Windows Firewall lacks outbound blocking, a staple of most third-party personal firewall products and, I believe, an absolute requirement. Inbound blocking -- something which all firewalls (including Microsoft's new one) do -- is what keeps illegitimate traffic from entering systems and networks through networking channels known as ports.
As Zone Labs' implementation of SP2 compatibility demonstrates, absence of outbound blocking isn't the only significant vulnerability in the Windows Firewall.