Just "Google" Vista's Firewall and you'll find mostly negitive reviews ... and for good reason. The "Inbound" component works much like the XP SP2 version, in that it passes the ShieldsUP test, however the "Outbound" component is de-activated. This means that all outbound traffic is permitted ... ouch!
Now you can activate the Outbound (block all traffic) however Microsoft does not provide any kind of prompt that something wants to make an outbound connection ... it just silently fails. I tried this method for several days and came to the conclusion that a "home-user" would trash their machine before they could figure out all the ins-and-outs.
Microsoft should have included the improved version of OneCare's Firewall interface in Vista.
So now what? ... most of the major Firewall programs are not Vista compatable yet ... duh! there are several of the so-called "Security Suites" that are compatable, but these are now considered "bloatware" ... I did test a freeware add-on "Vista Firewall Control" and found this works fairly well as a program alert. However it fails several basic leak tests including "ping" ... so it's not really ready for prime time.
Looks like we are in for a wait and see ... as with most new programs their first versions will have many problems and revisions. What a shame ... it doesn't look like SunBelt is going to make their Kerio Firewall "Vista compatable"?