I'm trying Windows Live OneCare, and for the moment, I like it. Though it requires a reboot, installation is smooth and it seems not too CPU intrusive. As expected, it requires me to acknowledge a few applications the first time they try to access the Internet, but I always wanted to try this kind of bidirectional firewall. Once a program is allowed, OneCare continues to inform me of Internet access in a non-intrusive way.
OneCare is much more than a firewall. In short, it's a firewall, an anti-virus and a hard drive tuner (backup, defrag, clean up).
As we expect from any "live" application, it stays up to date.
So in short, there's nothing new here, except for the anti-virus. They just regrouped tune-up and security services in one nice application... But what an ugly icon!!!