OK, I have been using Windows Live OneCare on my standalone laptop at home (my non-work machine) and I have to admit I have been impressed with how easy it is to forget it is there doing AV, Anti-spyware, Firewall and backups.
While I would still make use of other products to accomplish all the same functions on my own regardless of OneCare, Microsoft really has made the product just work pretty seamlessly. I am hard pressed to move off of it given how well things have gone. I have even restored files from the backup process (just to make sure things really work!)
Kudos to Microsoft on this one, it is by far the smoothest beta I have run to date.