This is great news. OneCare is one of my all-time-fave products. I love it because it was built knowing that the target user is no security expert. It wasn't built by geeks for geeks.
Everyone in my immediate family uses OneCare because (to quote my 70 year old father in law) "it's dead easy, simple and doesn't keep popping up messages I don't understand. I get green and stay green."
Windows Live OneCare 1.5 also works on Windows Vista, and yes, I will install it on my wife's computer :)
More info here.