A security suite from MS? Thanks but no, thanks.
I've never trusted MS much but since the Vista planetary scam (together with the hardware requirements fraud) they don't deserve the benefit of doubt.
First I'm not sure a rootkit is not included as a free gift. Second, their security track record is impressive, and third I do prefer the alternatives: Avira (free), NOD32/Bitdefender (commercial). Same for other apps: VLC, OpenOffice, Firefox, ...
Just my personal view.