I thought the anti-virus side of thing you have to buy a subscription for OneCare, which is a separate product outside Vista. As for the firewall, I'm sure Vista will have one, but a 'better' one is also available under OneCare. As to scanning for spyware, I think Windows Defender can do that, and it's free. If you've OneCare, Defender is incorporated.

I'm not entirely sure about what I wrote above, but I don't think you can totally get rid of third-party anti-virus software and totally rely on Vista.

I've been using Symantec for almost 10 years. This year, I've finally left it and switched to OneCare. While OneCare doesn't do everything Symantec can (I loved its ad blocking), OneCare has a much smaller footprint.